Random access coverage extension in wireless communications

ABSTRACT

Methods, systems, and devices for wireless communications are described that provide for aggregating random access requests across two or more physical random access channel (PRACH) occasions. Poor channel quality may inhibit the receipt of random access requests, and for user equipments (UEs) located in areas with relatively poor coverage, such aggregated random access requests may have an increased likelihood of successful receipt at a base station. The base station may configure a number of PRACH occasions to be available for aggregation of random access requests. A UE may receive PRACH configuration information from the base station, may aggregate a random access request across two or more PRACH occasions using the PRACH configuration information, and may transmit the aggregated random access request via the PRACH occasions. The base station may also configure one or more PRACH occasions to have a smaller subcarrier spacing for transmission of a random access request.

CROSS REFERENCES

The present Application for Patent claims the benefit of U.S.Provisional Patent Application No. 62/661,475 by ZHANG et al., entitled“RANDOM ACCESS COVERAGE EXTENSION IN WIRELESS COMMUNICATIONS,” filedApr. 23, 2018, assigned to the assignee hereof, and expresslyincorporated herein.

BACKGROUND

The following relates generally to wireless communications, and morespecifically to random access coverage extension in wirelesscommunications.

Wireless communications systems are widely deployed to provide varioustypes of communication content such as voice, video, packet data,messaging, broadcast, and so on. These systems may be capable ofsupporting communication with multiple users by sharing the availablesystem resources (e.g., time, frequency, and power). Examples of suchmultiple-access systems include fourth generation (4G) systems such asLong Term Evolution (LTE) systems, LTE-Advanced (LTE-A) systems, orLTE-A Pro systems, and fifth generation (5G) systems which may bereferred to as New Radio (NR) systems. These systems may employtechnologies such as code division multiple access (CDMA), time divisionmultiple access (TDMA), frequency division multiple access (FDMA),orthogonal frequency division multiple access (OFDMA), or discreteFourier transform-spread-OFDM (DFT-S-OFDM). A wireless multiple-accesscommunications system may include a number of base stations or networkaccess nodes, each simultaneously supporting communication for multiplecommunication devices, which may be otherwise known as user equipment(UE).

Some wireless communications systems may use wireless resources (e.g.,time resources, frequency resources, spatial resources, or combinationsthereof) for random access procedures to initiate connections between aUE and a base station. The random access procedures may include acontention based random access procedure where a device must contend forthe channel before attempting access or a contention free random accessprocedure where resources are preconfigured for the device. In somecases, the random access procedures may be performed using wirelessresources configured for a physical random access channel (PRACH) andmay involve exchanging one or more random access channel (RACH) signals,e.g., a RACH message 1 (msg1) which may be referred to as a randomaccess request, RACH message 2 (msg2), and the like. A random accessrequest may include a random access sequence or preamble that istransmitted to a base station.

SUMMARY

The described techniques relate to improved methods, systems, devices,and apparatuses that support random access coverage extension inwireless communications. Various described techniques provide foraggregating random access requests across two or more physical randomaccess channel (PRACH) occasions. In cases where channel quality betweena base station and a UE is relatively poor, the likelihood of successfulreceipt of a random access request at a base station may be reduced.Thus, techniques for enhancing the likelihood of successful receipt ofsuch random access requests may help to improve efficiency of wirelesscommunications systems. For example, a base station may configure PRACHresources that include a number of PRACH occasions, and some or all ofthe configured PRACH occasions may be available for aggregation ofrandom access requests. A user equipment (UE) may aggregate a randomaccess request across two or more PRACH occasions and may transmit theaggregated random access request via two or more PRACH occasions. Suchaggregated random access requests may provide increased likelihood ofsuccessful reception at the base station for UEs located in areas withrelatively poor coverage.

In some cases, a UE may determine to transmit a non-aggregated oraggregated random access request based on channel conditions measured atthe UE. In some cases, if a signal strength of a signal received at theUE from the base station (e.g., a synchronization signal block (SSB)transmission) is below a threshold value, the UE may transmit anaggregated random access request that spans two or more PRACH occasions.The two or more PRACH occasions may be contiguous or non-contiguous. Insome cases, the random access request may include a sequence or preamblethat is transmitted from the UE, and that may be selected from a set ofavailable preambles. In some cases, a first subset of preambles may beconfigured for aggregated random access requests, and a second subset ofpreambles may be configured for non-aggregated random access requests.Accordingly, the receiving base station may attempt to detect the firstsubset of preambles based on aggregated PRACH occasions and attempt todetect the second subset of preambles based on non-aggregated PRACHoccasions. In some cases, different PRACH occasions may use differentPRACH formats, and an aggregated random access request may span twoPRACH occasions that use different formats. Additionally oralternatively, random access coverage extension may be achieved throughreduced subcarrier spacing (SCS) for random access requests of certainPRACH occasions.

A method of wireless communication at a UE is described. The method mayinclude receiving, from a base station, PRACH configuration informationthat indicates a set of PRACH occasions available for aggregation ofrandom access requests and transmitting an aggregated random accessrequest via two or more PRACH occasions of the set of PRACH occasions.

An apparatus for wireless communication at a UE is described. Theapparatus may include a processor, memory in electronic communicationwith the processor, and instructions stored in the memory. Theinstructions may be executable by the processor to cause the apparatusto receive, from a base station, PRACH configuration information thatindicates a set of PRACH occasions available for aggregation of randomaccess requests and transmit an aggregated random access request via twoor more PRACH occasions of the set of PRACH occasions.

Another apparatus for wireless communication at a UE is described. Theapparatus may include means for receiving, from a base station, PRACHconfiguration information that indicates a set of PRACH occasionsavailable for aggregation of random access requests and transmitting anaggregated random access request via two or more PRACH occasions of theset of PRACH occasions.

A non-transitory computer-readable medium storing code for wirelesscommunication at a UE is described. The code may include instructionsexecutable by a processor to receive, from a base station, PRACHconfiguration information that indicates a set of PRACH occasionsavailable for aggregation of random access requests and transmit anaggregated random access request via two or more PRACH occasions of theset of PRACH occasions.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for measuring a signalstrength of a signal received from the base station and selecting theaggregated random access request for transmission based on the signalstrength being below a threshold value. In some examples of the method,apparatuses, and non-transitory computer-readable medium describedherein, the signal strength may be a reference signal received power(RSRP) measurement. In some examples of the method, apparatuses, andnon-transitory computer-readable medium described herein, the RSRPmeasurement may be measured from an SSB transmitted by the base station.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the set of PRACH occasionsthat are available for aggregation of random access requests includecontiguous PRACH occasions. In some examples of the method, apparatuses,and non-transitory computer-readable medium described herein, the set ofPRACH occasions that are available for aggregation of random accessrequests include non-contiguous PRACH occasions.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the PRACH configurationinformation further includes PRACH format information, and where a firstPRACH occasion of the set of PRACH occasions may have a first PRACHformat, and a second PRACH occasion of the set of PRACH occasions mayhave a second PRACH format.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the PRACH configurationinformation further indicates a set of available random accesspreambles, and where a first subset of the set of available randomaccess preambles are available for aggregated random access requests anda second subset of the set of available random access preambles areavailable for non-aggregated random access requests, the first subsetbeing non-overlapping with the second subset. In some examples of themethod, apparatuses, and non-transitory computer-readable mediumdescribed herein, a first subset of the set of PRACH occasions areavailable for transmission of aggregated random access requests, and asecond subset of the set of PRACH occasions are available fortransmission of non-aggregated random access requests, the first subsetbeing non-overlapping with the second subset.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, a first subset of the set ofPRACH occasions are available for transmission of aggregated randomaccess requests, and a second subset of the set of PRACH occasions areavailable for transmission of non-aggregated random access requests, thefirst subset at least partially overlapping with the second subset.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the receiving further mayinclude operations, features, means, or instructions for receiving aremaining minimum system information (RMSI) transmission from the basestation that includes the PRACH configuration information. In someexamples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the two or more PRACHoccasions for transmission of the aggregated random access request mapto a same SSB. In some examples of the method, apparatuses, andnon-transitory computer-readable medium described herein, the two ormore PRACH occasions for transmission of the aggregated random accessrequest span two or more PRACH configuration periods. In some examplesof the method, apparatuses, and non-transitory computer-readable mediumdescribed herein, the aggregated random access request includes a randomaccess preamble that spans each of the two or more PRACH occasions.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, a subset of the set of PRACHoccasions may have a first SCS that may be smaller than a second SCS ofother of the set of PRACH occasions. In some examples of the method,apparatuses, and non-transitory computer-readable medium describedherein, the first SCS provides a longer symbol duration relative to thesecond SCS.

A method of wireless communication is described. The method may includereceiving, from a base station, PRACH configuration information thatindicates a set of PRACH occasions available for transmission of randomaccess requests, where a first subset of the set of PRACH occasions areconfigured with a first SCS and a second subset of the set of PRACHoccasions are configured with a second SCS that is smaller than thefirst SCS, and where the second subset of the set of PRACH occasions areavailable for transmission of a CE random access request, selecting twoor more PRACH occasions of the second subset of PRACH occasions fortransmission of the CE random access request, and transmitting the CErandom access request via the selected two or more PRACH occasions.

An apparatus for wireless communication is described. The apparatus mayinclude a processor, memory in electronic communication with theprocessor, and instructions stored in the memory. The instructions maybe executable by the processor to cause the apparatus to receive, from abase station, PRACH configuration information that indicates a set ofPRACH occasions available for transmission of random access requests,where a first subset of the set of PRACH occasions are configured with afirst SCS and a second subset of the set of PRACH occasions areconfigured with a second SCS that is smaller than the first SCS, andwhere the second subset of the set of PRACH occasions are available fortransmission of a coverage extension random access request, select twoor more PRACH occasions of the second subset of PRACH occasions fortransmission of the CE random access request, and transmit the CE randomaccess request via the selected two or more PRACH occasions.

Another apparatus for wireless communication is described. The apparatusmay include means for receiving, from a base station, PRACHconfiguration information that indicates a set of PRACH occasionsavailable for transmission of random access requests, where a firstsubset of the set of PRACH occasions are configured with a first SCS anda second subset of the set of PRACH occasions are configured with asecond SCS that is smaller than the first SCS, and where the secondsubset of the set of PRACH occasions are available for transmission of aCE random access request, selecting two or more PRACH occasions of thesecond subset of PRACH occasions for transmission of the CE randomaccess request, and transmitting the CE random access request via theselected two or more PRACH occasions.

A non-transitory computer-readable medium storing code for wirelesscommunication is described. The code may include instructions executableby a processor to receive, from a base station, PRACH configurationinformation that indicates a set of PRACH occasions available fortransmission of random access requests, where a first subset of the setof PRACH occasions are configured with a first SCS and a second subsetof the set of PRACH occasions are configured with a second SCS that issmaller than the first SCS, and where the second subset of the set ofPRACH occasions are available for transmission of a CE random accessrequest, select two or more PRACH occasions of the second subset ofPRACH occasions for transmission of the CE random access request, andtransmit the CE random access request via the selected two or more PRACHoccasions.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the CE random access requesttransmitted via the second subset of PRACH occasions uses a same randomaccess format as a non-CE random access request transmitted via thefirst subset of PRACH occasions. In some examples of the method,apparatuses, and non-transitory computer-readable medium describedherein, the second SCS provides a longer symbol duration relative to thefirst SCS.

Some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein may further includeoperations, features, means, or instructions for measuring a signalstrength of a signal received from the base station and determining thatthe CE random access request may be to be transmitted based on thesignal strength being below a threshold value. In some examples of themethod, apparatuses, and non-transitory computer-readable mediumdescribed herein, the signal strength may be a RSRP measurement.

In some examples of the method, apparatuses, and non-transitorycomputer-readable medium described herein, the PRACH configurationinformation further includes aggregation information for at least aportion of the second subset of PRACH occasions that are available fortransmission of an aggregated random access request that spans at leasttwo PRACH occasions of the portion of the second subset of PRACHoccasions. In some examples of the method, apparatuses, andnon-transitory computer-readable medium described herein, the selectingfurther may include operations, features, means, or instructions forselecting the two or more PRACH occasions from the portion of the secondsubset of PRACH occasions that may be available for transmission of theaggregated random access request and transmitting the aggregated randomaccess request via the selected two or more PRACH occasions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of a wireless communications system thatsupports random access coverage extension in wireless communications inaccordance with aspects of the present disclosure.

FIG. 2 illustrates an example of a portion of a wireless communicationssystem that supports random access coverage extension in wirelesscommunications in accordance with aspects of the present disclosure.

FIG. 3 illustrates an example of PRACH formats that support randomaccess coverage extension in wireless communications in accordance withaspects of the present disclosure.

FIG. 4 illustrates an example of an aggregated random access requestthat supports random access coverage extension in wirelesscommunications in accordance with aspects of the present disclosure.

FIG. 5 illustrates an example of a resource configuration that supportsrandom access coverage extension in wireless communications inaccordance with aspects of the present disclosure.

FIG. 6 illustrates an example of a process that supports random accesscoverage extension in wireless communications in accordance with aspectsof the present disclosure.

FIG. 7 illustrates an example of a process flow that supports randomaccess coverage extension in wireless communications in accordance withaspects of the present disclosure.

FIGS. 8 and 9 show block diagrams of devices that support random accesscoverage extension in wireless communications in accordance with aspectsof the present disclosure.

FIG. 10 shows a block diagram of a device that supports random accesscoverage extension in wireless communications in accordance with aspectsof the present disclosure.

FIG. 11 shows a diagram of a system including a device that supportsrandom access coverage extension in wireless communications inaccordance with aspects of the present disclosure.

FIGS. 12 and 13 show block diagrams of devices that support randomaccess coverage extension in wireless communications in accordance withaspects of the present disclosure.

FIG. 14 shows a block diagram of a device that supports random accesscoverage extension in wireless communications in accordance with aspectsof the present disclosure.

FIG. 15 shows a diagram of a system including a device that supportsrandom access coverage extension in wireless communications inaccordance with aspects of the present disclosure.

FIGS. 16 through 18 show flowcharts illustrating methods that supportrandom access coverage extension in wireless communications inaccordance with aspects of the present disclosure.

DETAILED DESCRIPTION

As indicated above, some wireless communications systems may provideresources for random access procedures. For example, the network may useperiodic and/or aperiodic time/frequency resources that a user equipment(UE) may utilize to perform random access procedures. Various aspects ofthe present disclosure provide techniques for aggregating random accessrequests across two or more physical random access channel (PRACH)occasions. A base station may configure PRACH resources that include anumber of PRACH occasions, and some or all of the configured PRACHoccasions may be available for aggregation of random access requests.Additionally or alternatively, random access coverage extension may beachieved through reduced subcarrier spacing (SC S) for random accessrequests of certain PRACH occasions.

In some cases, random access requests may be transmitted according to anopen-loop power control scheme in which a first random access request istransmitted at a first power and, if a random access response is notreceived, a second random access request may be transmitted at a higherpower following a backoff period. In cases where a UE is located in anarea that has relatively poor coverage and poor channel conditions, orif directional beamforming parameters are mismatched, such repetitionsmay consume a relatively long period of time and still may not result ina successful transmission and receipt of a random access request. Insome cases, if a UE measures a received signal strength of atransmission from a base station (e.g., a synchronization signal block(SSB) transmission) to be below a threshold value, the UE may determineto transmit an aggregated random access request, which may enhance thelikelihood of successful receipt of the random access request at thebase station. Thus, system efficiency may be enhanced through moreefficient random access procedures. Further, power consumption andaccess time at a UE may be reduced through fewer repeated random accessrequest transmissions in cases where the UE measures a received signalstrength that is relatively low.

In cases where aggregated random access requests are configured, a UEmay aggregate a random access request across two or more PRACHoccasions. The UE may then transmit the aggregated random access requestvia the two or more PRACH occasions. In some cases, a UE may determinewhether to transmit non-aggregated or aggregated random access requestsbased on channel conditions measured at the UE. In some cases, if asignal strength of a signal received at the UE from the base station(e.g., an SSB transmission) is below a threshold value, the UE maytransmit an aggregated random access request that spans two or morePRACH occasions. The two or more PRACH occasions may be contiguous ornon-contiguous.

In some cases, the random access request may include a sequence orpreamble that is transmitted from the UE, which may be selected from aset of available preambles. In some cases, a first subset of preamblesmay be configured for aggregated random access requests, and a secondsubset of preambles may be configured for non-aggregated random accessrequests. In such cases, the receiving base station may attempt todetect the first subset of preambles based on aggregated PRACH occasionsand attempt to detect the second subset of preambles based onnon-aggregated PRACH occasions. In some cases, different PRACH occasionsmay use different PRACH formats, and an aggregated random access requestmay span two PRACH occasions that use different formats.

Aspects of the disclosure are initially described in the context ofwireless communications systems. Various examples of resources for, andtransmissions of, aggregated random access requests and SCS changes forrandom access requests are then described. Aspects of the disclosure arefurther illustrated by and described with reference to apparatusdiagrams, system diagrams, and flowcharts that relate to random accesscoverage extension in wireless communications.

FIG. 1 illustrates an example of a wireless communications system 100that supports random access coverage extension in wirelesscommunications in accordance with aspects of the present disclosure. Thewireless communications system 100 includes base stations 105, UEs 115,and a core network 130. In some examples, the wireless communicationssystem 100 may be a Long Term Evolution (LTE) network, an LTE-Advanced(LTE-A) network, an LTE-A Pro network, or a New Radio (NR) network. Insome cases, wireless communications system 100 may support enhancedbroadband communications, ultra-reliable (e.g., mission critical)communications, low latency communications, or communications withlow-cost and low-complexity devices. UEs 115 and base stations 105 mayemploy coverage extension techniques for random access requests inaccordance with various techniques discussed herein.

Base stations 105 may wirelessly communicate with UEs 115 via one ormore base station antennas. Base stations 105 described herein mayinclude or may be referred to by those skilled in the art as a basetransceiver station, a radio base station, an access point, a radiotransceiver, a NodeB, an eNodeB (eNB), a next-generation Node B orgiga-nodeB (either of which may be referred to as a gNB), a Home NodeB,a Home eNodeB, or some other suitable terminology. Wirelesscommunications system 100 may include base stations 105 of differenttypes (e.g., macro or small cell base stations). The UEs 115 describedherein may be able to communicate with various types of base stations105 and network equipment including macro eNBs, small cell eNBs, gNBs,relay base stations, and the like.

Each base station 105 may be associated with a particular geographiccoverage area 110 in which communications with various UEs 115 issupported. Each base station 105 may provide communication coverage fora respective geographic coverage area 110 via communication links 125,and communication links 125 between a base station 105 and a UE 115 mayutilize one or more carriers. Communication links 125 shown in wirelesscommunications system 100 may include uplink transmissions from a UE 115to a base station 105, or downlink transmissions from a base station 105to a UE 115. Downlink transmissions may also be called forward linktransmissions while uplink transmissions may also be called reverse linktransmissions.

The geographic coverage area 110 for a base station 105 may be dividedinto sectors making up only a portion of the geographic coverage area110, and each sector may be associated with a cell. For example, eachbase station 105 may provide communication coverage for a macro cell, asmall cell, a hot spot, or other types of cells, or various combinationsthereof In some examples, a base station 105 may be movable andtherefore provide communication coverage for a moving geographiccoverage area 110. In some examples, different geographic coverage areas110 associated with different technologies may overlap, and overlappinggeographic coverage areas 110 associated with different technologies maybe supported by the same base station 105 or by different base stations105. The wireless communications system 100 may include, for example, aheterogeneous LTE/LTE-A/LTE-A Pro or NR network in which different typesof base stations 105 provide coverage for various geographic coverageareas 110.

The term “cell” refers to a logical communication entity used forcommunication with a base station 105 (e.g., over a carrier), and may beassociated with an identifier for distinguishing neighboring cells(e.g., a physical cell identifier (PCID), a virtual cell identifier(VCID)) operating via the same or a different carrier. In some examples,a carrier may support multiple cells, and different cells may beconfigured according to different protocol types (e.g., machine-typecommunication (MTC), narrowband Internet-of-Things (NB-IoT), enhancedmobile broadband (eMBB), or others) that may provide access fordifferent types of devices. In some cases, the term “cell” may refer toa portion of a geographic coverage area 110 (e.g., a sector) over whichthe logical entity operates.

UEs 115 may be dispersed throughout the wireless communications system100, and each UE 115 may be stationary or mobile. A UE 115 may also bereferred to as a mobile device, a wireless device, a remote device, ahandheld device, or a subscriber device, or some other suitableterminology, where the “device” may also be referred to as a unit, astation, a terminal, or a client. A UE 115 may also be a personalelectronic device such as a cellular phone, a personal digital assistant(PDA), a tablet computer, a laptop computer, or a personal computer. Insome examples, a UE 115 may also refer to a wireless local loop (WLL)station, an Internet of Things (IoT) device, an Internet of Everything(IoE) device, or an MTC device, or the like, which may be implemented invarious articles such as appliances, vehicles, meters, or the like.

Some UEs 115, such as MTC or IoT devices, may be low cost or lowcomplexity devices, and may provide for automated communication betweenmachines (e.g., via Machine-to-Machine (M2M) communication). M2Mcommunication or MTC may refer to data communication technologies thatallow devices to communicate with one another or a base station 105without human intervention. In some examples, M2M communication or MTCmay include communications from devices that integrate sensors or metersto measure or capture information and relay that information to acentral server or application program that can make use of theinformation or present the information to humans interacting with theprogram or application. Some UEs 115 may be designed to collectinformation or enable automated behavior of machines. Examples ofapplications for MTC devices include smart metering, inventorymonitoring, water level monitoring, equipment monitoring, healthcaremonitoring, wildlife monitoring, weather and geological eventmonitoring, fleet management and tracking, remote security sensing,physical access control, and transaction-based business charging. Insome cases, such MTC devices may be located in areas that haverelatively poor channel conditions, such as within a facility that hasrelatively dense objects that may interfere with wireless transmissions.In such cases, coverage extension techniques, including random accesscoverage extension techniques such as discussed herein, may provide forenhanced reliability of communications.

Some UEs 115 may be configured to employ operating modes that reducepower consumption, such as half-duplex communications (e.g., a mode thatsupports one-way communication via transmission or reception, but nottransmission and reception simultaneously). In some examples half-duplexcommunications may be performed at a reduced peak rate. Other powerconservation techniques for UEs 115 include entering a power saving“deep sleep” mode when not engaging in active communications, oroperating over a limited bandwidth (e.g., according to narrowbandcommunications). In some cases, UEs 115 may be designed to supportcritical functions (e.g., mission critical functions), and a wirelesscommunications system 100 may be configured to provide ultra-reliablecommunications for these functions. In such cases, efficient andreliable connection establishment, such as initiated via random accessrequests, may be important for system operation.

In some cases, a UE 115 may also be able to communicate directly withother UEs 115 (e.g., using a peer-to-peer (P2P) or device-to-device(D2D) protocol). One or more of a group of UEs 115 utilizing D2Dcommunications may be within the geographic coverage area 110 of a basestation 105. Other UEs 115 in such a group may be outside the geographiccoverage area 110 of a base station 105, or be otherwise unable toreceive transmissions from a base station 105. In some cases, groups ofUEs 115 communicating via D2D communications may utilize a one-to-many(1:M) system in which each UE 115 transmits to every other UE 115 in thegroup. In some cases, a base station 105 facilitates the scheduling ofresources for D2D communications. In other cases, D2D communications arecarried out between UEs 115 without the involvement of a base station105.

Base stations 105 may communicate with the core network 130 and with oneanother. For example, base stations 105 may interface with the corenetwork 130 through backhaul links 132 (e.g., via an S1 or otherinterface). Base stations 105 may communicate with one another overbackhaul links 134 (e.g., via an X2 or other interface) either directly(e.g., directly between base stations 105) or indirectly (e.g., via corenetwork 130).

The core network 130 may provide user authentication, accessauthorization, tracking, Internet Protocol (IP) connectivity, and otheraccess, routing, or mobility functions. The core network 130 may be anevolved packet core (EPC), which may include at least one mobilitymanagement entity (MME), at least one serving gateway (S-GW), and atleast one Packet Data Network (PDN) gateway (P-GW). The MME may managenon-access stratum (e.g., control plane) functions such as mobility,authentication, and bearer management for UEs 115 served by basestations 105 associated with the EPC. User IP packets may be transferredthrough the S-GW, which itself may be connected to the P-GW. The P-GWmay provide IP address allocation as well as other functions. The P-GWmay be connected to the network operators IP services. The operators IPservices may include access to the Internet, Intranet(s), an IPMultimedia Subsystem (IMS), or a Packet-Switched (PS) Streaming Service.

At least some of the network devices, such as a base station 105, mayinclude subcomponents such as an access network entity, which may be anexample of an access node controller (ANC). Each access network entitymay communicate with UEs 115 through a number of other access networktransmission entities, which may be referred to as a radio head, a smartradio head, or a transmission/reception point (TRP). In someconfigurations, various functions of each access network entity or basestation 105 may be distributed across various network devices (e.g.,radio heads and access network controllers) or consolidated into asingle network device (e.g., a base station 105).

Wireless communications system 100 may operate using one or morefrequency bands, typically in the range of 300 MHz to 300 GHz.Generally, the region from 300 MHz to 3 GHz is known as the ultra-highfrequency (UHF) region or decimeter band, since the wavelengths rangefrom approximately one decimeter to one meter in length. UHF waves maybe blocked or redirected by buildings and environmental features.However, the waves may penetrate structures sufficiently for a macrocell to provide service to UEs 115 located indoors. Transmission of UHFwaves may be associated with smaller antennas and shorter range (e.g.,less than 100 km) compared to transmission using the smaller frequenciesand longer waves of the high frequency (HF) or very high frequency (VHF)portion of the spectrum below 300 MHz.

Wireless communications system 100 may also operate in a super highfrequency (SHF) region using frequency bands from 3 GHz to 30 GHz, alsoknown as the centimeter band. The SHF region includes bands such as the5 GHz industrial, scientific, and medical (ISM) bands, which may be usedopportunistically by devices that can tolerate interference from otherusers.

Wireless communications system 100 may also operate in an extremely highfrequency (EHF) region of the spectrum (e.g., from 30 GHz to 300 GHz),also known as the millimeter band. In some examples, wirelesscommunications system 100 may support millimeter wave (mmW)communications between UEs 115 and base stations 105, and EHF antennasof the respective devices may be even smaller and more closely spacedthan UHF antennas. In some cases, this may facilitate use of antennaarrays within a UE 115. However, the propagation of EHF transmissionsmay be subject to even greater atmospheric attenuation and shorter rangethan SHF or UHF transmissions. Techniques disclosed herein may beemployed across transmissions that use one or more different frequencyregions, and designated use of bands across these frequency regions maydiffer by country or regulating body.

In some cases, wireless communications system 100 may utilize bothlicensed and unlicensed radio frequency spectrum bands. For example,wireless communications system 100 may employ License Assisted Access(LAA), LTE-Unlicensed (LTE-U) radio access technology, or NR technologyin an unlicensed band such as the 5 GHz ISM band. When operating inunlicensed radio frequency spectrum bands, wireless devices such as basestations 105 and UEs 115 may employ listen-before-talk (LBT) proceduresto ensure a frequency channel is clear before transmitting data. In somecases, operations in unlicensed bands may be based on a CA configurationin conjunction with CCs operating in a licensed band (e.g., LAA).Operations in unlicensed spectrum may include downlink transmissions,uplink transmissions, peer-to-peer transmissions, or a combination ofthese. Duplexing in unlicensed spectrum may be based on frequencydivision duplexing (FDD), time division duplexing (TDD), or acombination of both.

In some examples, base station 105 or UE 115 may be equipped withmultiple antennas, which may be used to employ techniques such astransmit diversity, receive diversity, multiple-input multiple-output(MIMO) communications, or beamforming. For example, wirelesscommunications system 100 may use a transmission scheme between atransmitting device (e.g., a base station 105) and a receiving device(e.g., a UE 115), where the transmitting device is equipped withmultiple antennas and the receiving devices are equipped with one ormore antennas. MIMO communications may employ multipath signalpropagation to increase the spectral efficiency by transmitting orreceiving multiple signals via different spatial layers, which may bereferred to as spatial multiplexing. The multiple signals may, forexample, be transmitted by the transmitting device via differentantennas or different combinations of antennas. Likewise, the multiplesignals may be received by the receiving device via different antennasor different combinations of antennas. Each of the multiple signals maybe referred to as a separate spatial stream and may carry bitsassociated with the same data stream (e.g., the same codeword) ordifferent data streams. Different spatial layers may be associated withdifferent antenna ports used for channel measurement and reporting. MIMOtechniques include single-user MIMO (SU-MIMO) where multiple spatiallayers are transmitted to the same receiving device, and multiple-userMIMO (MU-MIMO) where multiple spatial layers are transmitted to multipledevices.

Beamforming, which may also be referred to as spatial filtering,directional transmission, or directional reception, is a signalprocessing technique that may be used at a transmitting device or areceiving device (e.g., a base station 105 or a UE 115) to shape orsteer an antenna beam (e.g., a transmit beam or receive beam) along aspatial path between the transmitting device and the receiving device.Beamforming may be achieved by combining the signals communicated viaantenna elements of an antenna array such that signals propagating atparticular orientations with respect to an antenna array experienceconstructive interference while others experience destructiveinterference. The adjustment of signals communicated via the antennaelements may include a transmitting device or a receiving deviceapplying certain amplitude and phase offsets to signals carried via eachof the antenna elements associated with the device. The adjustmentsassociated with each of the antenna elements may be defined by abeamforming weight set associated with a particular orientation (e.g.,with respect to the antenna array of the transmitting device orreceiving device, or with respect to some other orientation).

In one example, a base station 105 may use multiple antennas or antennaarrays to conduct beamforming operations for directional communicationswith a UE 115. For instance, some signals (e.g. synchronization signals,reference signals, beam selection signals, or other control signals) maybe transmitted by a base station 105 multiple times in differentdirections, which may include a signal being transmitted according todifferent beamforming weight sets associated with different directionsof transmission. Transmissions in different beam directions may be usedto identify (e.g., by the base station 105 or a receiving device, suchas a UE 115) a beam direction for subsequent transmission and/orreception by the base station 105. Some signals, such as data signalsassociated with a particular receiving device, may be transmitted by abase station 105 in a single beam direction (e.g., a directionassociated with the receiving device, such as a UE 115). In someexamples, the beam direction associated with transmissions along asingle beam direction may be determined based at least in part on asignal that was transmitted in different beam directions. For example, aUE 115 may receive one or more of the signals transmitted by the basestation 105 in different directions, and the UE 115 may report to thebase station 105 an indication of the signal the UE 115 received with ahighest signal quality, or an otherwise acceptable signal quality.Although these techniques are described with reference to signalstransmitted in one or more directions by a base station 105, a UE 115may employ similar techniques for transmitting signals multiple times indifferent directions (e.g., for identifying a beam direction forsubsequent transmission or reception by the UE 115), or transmitting asignal in a single direction (e.g., for transmitting data to a receivingdevice).

A receiving device (e.g., a UE 115, which may be an example of a mmWreceiving device) may try multiple receive beams when receiving varioussignals from the base station 105, such as synchronization signals,reference signals, beam selection signals, or other control signals. Forexample, a receiving device may try multiple receive directions byreceiving via different antenna subarrays, by processing receivedsignals according to different antenna subarrays, by receiving accordingto different receive beamforming weight sets applied to signals receivedat a plurality of antenna elements of an antenna array, or by processingreceived signals according to different receive beamforming weight setsapplied to signals received at a plurality of antenna elements of anantenna array, any of which may be referred to as “listening” accordingto different receive beams or receive directions. In some examples areceiving device may use a single receive beam to receive along a singlebeam direction (e.g., when receiving a data signal). The single receivebeam may be aligned in a beam direction determined based on listeningaccording to different receive beam directions (e.g., a beam directiondetermined to have a highest signal strength, highest signal-to-noiseratio, or otherwise acceptable signal quality based on listeningaccording to multiple beam directions).

In some cases, the antennas of a base station 105 or UE 115 may belocated within one or more antenna arrays, which may support MIMOoperations, or transmit or receive beamforming. For example, one or morebase station antennas or antenna arrays may be co-located at an antennaassembly, such as an antenna tower. In some cases, antennas or antennaarrays associated with a base station 105 may be located in diversegeographic locations. A base station 105 may have an antenna array witha number of rows and columns of antenna ports that the base station 105may use to support beamforming of communications with a UE 115.Likewise, a UE 115 may have one or more antenna arrays that may supportvarious MIMO or beamforming operations.

In some cases, wireless communications system 100 may be a packet-basednetwork that operate according to a layered protocol stack. In the userplane, communications at the bearer or Packet Data Convergence Protocol(PDCP) layer may be IP-based. A Radio Link Control (RLC) layer may insome cases perform packet segmentation and reassembly to communicateover logical channels. A Medium Access Control (MAC) layer may performpriority handling and multiplexing of logical channels into transportchannels. The MAC layer may also use hybrid automatic repeat request(HARQ) to provide retransmission at the MAC layer to improve linkefficiency. In the control plane, the Radio Resource Control (RRC)protocol layer may provide establishment, configuration, and maintenanceof an RRC connection between a UE 115 and a base station 105 or corenetwork 130 supporting radio bearers for user plane data. At thePhysical (PHY) layer, transport channels may be mapped to physicalchannels.

Time intervals in LTE or NR may be expressed in multiples of a basictime unit, which may, for example, refer to a sampling period ofT_(s)=1/30,720,000 seconds. Time intervals of a communications resourcemay be organized according to radio frames each having a duration of 10milliseconds (ms), where the frame period may be expressed asT_(f)=307,200 T_(s). The radio frames may be identified by a systemframe number (SFN) ranging from 0 to 1023. Each frame may include 10subframes numbered from 0 to 9, and each subframe may have a duration of1 ms. A subframe may be further divided into 2 slots each having aduration of 0.5 ms, and each slot may contain 6 or 7 modulation symbolperiods (e.g., depending on the length of the cyclic prefix prepended toeach symbol period). Excluding the cyclic prefix, each symbol period maycontain 2048 sampling periods. In some cases, a subframe may be thesmallest scheduling unit of the wireless communications system 100, andmay be referred to as a transmission time interval (TTI). In othercases, a smallest scheduling unit of the wireless communications system100 may be shorter than a subframe or may be dynamically selected (e.g.,in bursts of shortened TTIs (sTTIs) or in selected component carriersusing sTTIs).

In some wireless communications systems, a slot may further be dividedinto multiple mini-slots containing one or more symbols. In someinstances, a symbol of a mini-slot or a mini-slot may be the smallestunit of scheduling. Each symbol may vary in duration depending on thesubcarrier spacing or frequency band of operation, for example. Further,some wireless communications systems may implement slot aggregation inwhich multiple slots or mini-slots are aggregated together and used forcommunication between a UE 115 and a base station 105.

The term “carrier” refers to a set of radio frequency spectrum resourceshaving a defined physical layer structure for supporting communicationsover a communication link 125. For example, a carrier of a communicationlink 125 may include a portion of a radio frequency spectrum band thatis operated according to physical layer channels for a given radioaccess technology. Each physical layer channel may carry user data,control information, or other signaling. A carrier may be associatedwith a pre-defined frequency channel (e.g., an E-UTRA absolute radiofrequency channel number (EARFCN)), and may be positioned according to achannel raster for discovery by UEs 115. Carriers may be downlink oruplink (e.g., in an FDD mode), or be configured to carry downlink anduplink communications (e.g., in a TDD mode). In some examples, signalwaveforms transmitted over a carrier may be made up of multiplesub-carriers (e.g., using multi-carrier modulation (MCM) techniques suchas orthogonal frequency division multiplexing (OFDM) or DFT-s-OFDM).

The organizational structure of the carriers may be different fordifferent radio access technologies (e.g., LTE, LTE-A, LTE-A Pro, NR,etc.). For example, communications over a carrier may be organizedaccording to TTIs or slots, each of which may include user data as wellas control information or signaling to support decoding the user data. Acarrier may also include dedicated acquisition signaling (e.g.,synchronization signals or system information, etc.) and controlsignaling that coordinates operation for the carrier. In some examples(e.g., in a carrier aggregation configuration), a carrier may also haveacquisition signaling or control signaling that coordinates operationsfor other carriers.

Physical channels may be multiplexed on a carrier according to varioustechniques. A physical control channel and a physical data channel maybe multiplexed on a downlink carrier, for example, using time divisionmultiplexing (TDM) techniques, frequency division multiplexing (FDM)techniques, or hybrid TDM-FDM techniques. In some examples, controlinformation transmitted in a physical control channel may be distributedbetween different control regions in a cascaded manner (e.g., between acommon control region or common search space and one or more UE-specificcontrol regions or UE-specific search spaces).

A carrier may be associated with a particular bandwidth of the radiofrequency spectrum, and in some examples the carrier bandwidth may bereferred to as a “system bandwidth” of the carrier or the wirelesscommunications system 100. For example, the carrier bandwidth may be oneof a number of predetermined bandwidths for carriers of a particularradio access technology (e.g., 1.4, 3, 5, 10, 15, 20, 40, or 80 MHz). Insome examples, each served UE 115 may be configured for operating overportions or all of the carrier bandwidth. In other examples, some UEs115 may be configured for operation using a narrowband protocol typethat is associated with a predefined portion or range (e.g., set ofsubcarriers or RBs) within a carrier (e.g., “in-band” deployment of anarrowband protocol type).

In a system employing MCM techniques, a resource element may consist ofone symbol period (e.g., a duration of one modulation symbol) and onesubcarrier, where the symbol period and subcarrier spacing are inverselyrelated. The number of bits carried by each resource element may dependon the modulation scheme (e.g., the order of the modulation scheme).Thus, the more resource elements that a UE 115 receives and the higherthe order of the modulation scheme, the higher the data rate may be forthe UE 115. In MIMO systems, a wireless communications resource mayrefer to a combination of a radio frequency spectrum resource, a timeresource, and a spatial resource (e.g., spatial layers), and the use ofmultiple spatial layers may further increase the data rate forcommunications with a UE 115.

In some cases, wireless communications system 100 may utilize enhancedcomponent carriers (eCCs). An eCC may be characterized by one or morefeatures including wider carrier or frequency channel bandwidth, shortersymbol duration, shorter TTI duration, or modified control channelconfiguration. In some cases, an eCC may be associated with a carrieraggregation configuration or a dual connectivity configuration (e.g.,when multiple serving cells have a suboptimal or non-ideal backhaullink). An eCC may also be configured for use in unlicensed spectrum orshared spectrum (e.g., where more than one operator is allowed to usethe spectrum). An eCC characterized by wide carrier bandwidth mayinclude one or more segments that may be utilized by UEs 115 that arenot capable of monitoring the whole carrier bandwidth or are otherwiseconfigured to use a limited carrier bandwidth (e.g., to conserve power).

In some cases, an eCC may utilize a different symbol duration than otherCCs, which may include use of a reduced symbol duration as compared withsymbol durations of the other CCs. A shorter symbol duration may beassociated with increased spacing between adjacent subcarriers. Adevice, such as a UE 115 or base station 105, utilizing eCCs maytransmit wideband signals (e.g., according to frequency channel orcarrier bandwidths of 20, 40, 60, 80 MHz, etc.) at reduced symboldurations (e.g., 16.67 microseconds). A TTI in eCC may consist of one ormultiple symbol periods. In some cases, the TTI duration (that is, thenumber of symbol periods in a TTI) may be variable.

In some cases, a base station 105 may configure PRACH resources thatinclude a number of PRACH occasions, where some or all of the configuredPRACH occasions may be available for aggregation of random accessrequests. A UE 115 may aggregate a random access request across two ormore PRACH occasions and may transmit the aggregated random accessrequest via the two or more PRACH occasions. Such aggregated randomaccess requests may provide increased likelihood of successful receptionat the base station 105 for UEs 115 located in areas with relativelypoor coverage. Additionally or alternatively, random access coverageextension may be achieved through reduced SCS for random access requestsof certain PRACH occasions.

FIG. 2 illustrates an example of a wireless communications system 200that supports random access coverage extension in wirelesscommunications in accordance with aspects of the present disclosure. Insome examples, wireless communications system 200 may implement aspectsof wireless communications system 100. In some examples, the wirelesscommunications system 200 may include a base station 105-a and UE 115-a,which may be examples of the corresponding devices as described withreference to FIG. 1. The UE 115-a may communicate with the base station105-a within a coverage area 110-a.

In some examples, the base station 105-a may transmit downlinktransmissions 205 to the UE 115-a, and the UE 115-a may transmit uplinktransmissions 210 to the base station. The downlink transmissions 205and uplink transmissions 210 may be made via one or more carriers. Insome examples, the downlink transmissions 205 and uplink transmissions210 may be beamformed transmissions using mmW frequencies. As indicatedabove, the base station 105-a may configure resources for various uplinkand downlink transmissions, including a physical downlink controlchannel (PDCCH), a physical downlink shared channel (PDSCH)transmissions, a physical uplink control channel (PUCCH), a physicaluplink shared channel (PUSCH), and a PRACH, among others. The variousconfigurations may be provided to UEs 115 within coverage area 110-a viabroadcast transmissions, such as periodic SSB transmissions andremaining minimum system information (RMSI) transmissions, where the SSBor RMSI transmissions may include PRACH configuration 215. The UE 115-amay detect the SSB transmissions, determine the PRACH configuration 215,and identify configured PRACH occasions that are available fortransmitting a random access request 220. Random access request 220 maybe used for initial system access or, in some cases, for reestablishinga connection following an idle period.

In some cases, the random access request 220 may include a random accesspreamble that the UE 115-a selects from a set of available random accesspreambles. The set of available random access preambles may bepredefined and may include bit sequences that may be used to identifythe UE 115-a in random access transmissions. In some cases, the PRACHconfiguration 215 may identify a PRACH format that provides a number ofsymbols and indicates random access preambles that may be used by the UE115-a. In some NR systems, a short sequence based preamble may be used,in which a number of short sequences are repeated over the number ofsymbols of a PRACH occasion. In some cases, different PRACH occasionsmay have different PRACH formats.

As indicated above, in some examples, the UE 115-a may experiencerelatively poor channel conditions that may reduce the likelihood of therandom access request 220 being successfully received at the basestation 105-a. For example, the UE 115-a may be in a location that hasrelatively poor coverage. In examples where the UE 115-a and basestation 105-a use beamformed transmissions, during an initial accessstage, beamforming gain may be limited because the base station 105-aand UE 115-a have not performed beam refinement procedures. Accordingly,the base station 105-a may use beamforming parameters to receive uplinkrandom access requests 220 over a relatively wide beam in order toreduce PRACH overhead. In such cases, the UE 115-a may experiencerelatively poor channel conditions due to beam mismatch. Random accesscoverage extension techniques discussed herein may enhance thelikelihood of the base station 105-a successfully receiving the randomaccess request 220 in cases where the UE 115-a experiences relativelypoor channel conditions.

In some cases, random access coverage extension may be achieved throughaggregation of random access request 220 over two or more PRACHoccasions. The base station 105-a may identify that the random accessrequest 220 is aggregated over the two or more PRACH occasions, maycombine signals received during each occasion, and may attempt to decodethe combined signals. An aggregated random access request may includerandom access preambles that are concatenated to span PRACH resources ofthe two or more PRACH occasions. In some cases, an aggregated randomaccess request may also be referred to as an extended random accessrequest or an extended PRACH.

In some cases, the UE 115-a may determine whether to transmit anon-aggregated or an aggregated random access request 220 based onchannel conditions measured at the UE 115-a. In some examples, if asignal strength of a signal received at the UE 115-a from the basestation 105-a (e.g., an SSB transmission) is below a threshold value,the UE 115-a may transmit an aggregated random access request 220 thatspans two or more PRACH occasions. The two or more PRACH occasions maybe contiguous or non-contiguous. In some cases, a first subset ofpreambles may be configured (e.g., via an indication in PRACHconfiguration 215) for aggregated random access requests, and a secondsubset of preambles may be configured for non-aggregated random accessrequests. In such cases, the base station 105-a may attempt to detectthe first subset of preambles based on aggregated PRACH occasions andattempt to detect the second subset of preambles based on non-aggregatedPRACH occasions. In some cases, different PRACH occasions may usedifferent PRACH formats, and the aggregated random access request 220may span two PRACH occasions that use different formats.

Additionally or alternatively, random access coverage extension may beachieved through reduced SCS of certain PRACH occasions for the randomaccess request 220. In such cases a first SCS, such as a 15 kHz or 30kHz SCS may be configured for a first subset of PRACH occasions, and asecond SCS that is smaller than the first SCS (e.g., a reduced SCS),such as a 7.5 kHz or 15 kHz SCS, may be configured for a second subsetof PRACH occasions. In some examples, the UE 115-a may determine to usecoverage extension for random access request 220 and may select a PRACHoccasion from the second subset of PRACH occasions. The reduced SCS, fora given PRACH format, may result in the random access request 220spanning a longer time duration. In some cases, this may allow the basestation 105-a to collect more power from the random access request 220and thereby enhance the likelihood that the base station 105-a willsuccessfully receive and decode the random access request 220. In somecases, the reduced SCS may be used in conjunction with aggregated randomaccess requests 220.

FIG. 3 illustrates an example of PRACH formats 300 that support randomaccess coverage extension in wireless communications in accordance withaspects of the present disclosure. In some examples, PRACH formats 300may implement aspects of wireless communications systems 100 or 200. Forexample, a number of different formats may be available for selection ofa PRACH format 300 for one or more PRACH occasions. In some cases, thePRACH formats 300 may include a number of A formats 305 (formats A0through A3), a number of B formats 310 (format B1 through B4), and anumber of C formats 315. Different PRACH formats 300 may have differentcyclic prefix 320 durations, and different guard times 325 (e.g., whichmay include guard times equal to zero).

The PRACH formats 300 may include short sequence based preambles, inwhich a same short sequence is repeated in each symbol of the PRACHoccasion following the cyclic prefix 320. In some cases, the shortsequences may have a length of 139 elements in the Zadoff-Chu sequenceand, based on a 15 kHz SCS, may each have a duration of 66.67 μs andhave a bandwidth of 2.16 MHz. For other SCSs, such as 30 kHz, 60 kHz, or120 kHz SCS, the preamble formats may be scaled according to the SCS,resulting in a shorter-duration sequence relative to the 15 kHz SCS. Forexample, 1, 2, 4, 6 or 12 OFDM symbols may be configured for a PRACHoccasion, with cyclic prefix 320 aggregated at a beginning of the burst,and with or without guard time 325 at the end. In cases where one ormore data channels are configured to have a same numerology as the PRACHpreambles, the PRACH preambles may be aligned with OFDM symbolboundaries of the one or more data channels. As indicated above, in somecases a UE may aggregate random access requests to span two or morePRACH occasions, as will be discussed in more detail with reference toFIG. 4. Additionally or alternatively, different PRACH occasions may beconfigured with smaller SCS that may be selected for random accesscoverage extension, as will be discussed in more detail with referenceto FIG. 5.

FIG. 4 illustrates an example of an aggregated random access request 400that supports random access coverage extension in wirelesscommunications in accordance with aspects of the present disclosure. Insome examples, aggregated random access request 400 may implementaspects of wireless communications system 100 or 200. For example, anextended PRACH occasion 405 may be configured to span a first PRACHoccasion 410 and a second PRACH occasion 415. Within each PRACH occasion410 and 415, a random access preamble may be transmitted in accordancewith the PRACH format associated with the PRACH occasion, where thePRACH format may include one or more sort sequences 420, a cyclic prefix425, and, in some cases, a guard time.

The concatenation or aggregation of the first PRACH occasion 410 andsecond PRACH occasion 415 may form an extended PRACH occasion 405. WhileFIG. 4 illustrates two PRACH occasions, other examples may include threeor more PRACH occasions. The first PRACH occasion 410 and the secondPRACH occasion 415 may be contiguous or non-contiguous PRACH occasions.For example, the first PRACH occasion 410 may be located in a firstslot, the second PRACH occasion 415 may be located in a second slot, andthe PRACH occasions 410 and 415 may be aggregated to form an extendedPRACH occasion 405. In other cases, the first PRACH occasion 410 mayimmediately precede the second PRACH occasion 415 (and thus the secondPRACH occasion 415 may be immediately subsequent to the first PRACHoccasion 410) in a same slot. In some cases, the first PRACH occasion410 and the second PRACH occasion 415 may each have a same PRACH format(e.g., each may have PRACH format A3). In other cases, the first PRACHoccasion 410 and the second PRACH occasion 415 may have different PRACHformats. For example, the first PRACH occasion 410 may have PRACH formatA3 and the second PRACH occasion 415 may have PRACH format B3, althoughany combination of PRACH formats may be used.

In some cases, the preamble sequences used for extended random accessrequests (e.g., via random access request aggregation, reduced SCS, orcombinations thereof) may be a subset of a set of available preamblesequences. For example, a base station may configure a first subset ofpreambles in the PRACH occasions for enhanced coverage support throughextended random access requests, and may configure a second subset ofpreambles for non-enhanced coverage support. Additionally oralternatively, a first subset of PRACH occasions may be configured forextended random access requests and a second subset of PRACH occasionsmay be configured for regular, non-extended random access requests. Insome cases, the first subset of PRACH occasions may not overlap with thesecond subset of PRACH occasions, and a base station may identifyextended random access requests based on the subset of PRACH occasionsused for transmission. In other cases, the first subset of PRACHoccasions may at least partially overlap with the second subset of PRACHoccasions.

As such, different preambles may be configured for extended versusnon-extended random access requests, where the base station may attemptto detect extended random access requests based on aggregated PRACHoccasions, and may attempt to detect the non-extended random accessrequest based on a single PRACH occasion. In some cases, the preamblesequences and the PRACH occasions for extended random access requestsmay be indicated by the base station in RMSI (e.g., a mask intime/preambles to allow the aggregation).

In some cases, multiple aggregated PRACH occasions may map to a same SSBfor random access request extension. In some cases, one SSB, which maycorrespond to one PRACH configuration period, may be configured to spanmultiple PRACH occasions, where two or more of the multiple PRACHoccasions may be configured for extended random access requests. Forexample, one SSB may map to eight PRACH occasions, and two or more ofthe eight PRACH occasions may be configured for extended random accessrequests. In other cases, two SSBs may map to a single PRACH occasion,and the two or more PRACH occasions 410 and 415 for transmission of theaggregated random access request may span two or more PRACHconfiguration periods. In some cases, a cyclic mapping of SSBs to PRACHoccasions may be provided during a time period, where the time periodmay span one or more PRACH configuration periods and the cyclic mappingmay be used to effectively realize the same SSB mapping to multiple RACHoccasions.

When the UE selects the random access preamble in the extended format,the UE may repeat the preamble to span all concatenated PRACH occasionsaccordingly. As indicated above, the UE may select an extended ornon-extended PRACH format based on channel conditions. For example, theUE may measure a reference signal received power (RSRP) of a referencesignal in an SSB received from the base station. If the measured RSRP isbelow a threshold value, the UE may select an extended PRACH format, andif the measured RSRP is at or above the threshold value, the UE mayselect a non-extended or non-aggregated PRACH format.

FIG. 5 illustrates an example of a resource configuration 500 thatsupports random access coverage extension in wireless communications inaccordance with aspects of the present disclosure. In some examples,resource configuration 500 may implement aspects of wirelesscommunications system 100 or 200.

In some aspects, resource configuration 500 may support configuring oftime-frequency regions for PRACH occasions. In some cases, PRACHoccasions may be configured to be periodic in time. For example, PRACHoccasions may be configured in radio frame 505-a, 505-c, and 505-e thatmay correspond to radio frames 505 that are alternating in time. It isto be understood that other periodicities may be configured, and thisexample is for purposes of discussion and illustration only. In somecases, the plurality of radio frames 505 may each include a plurality ofsubframes 510, each subframe 510 including a plurality of slots 515, andeach slot 515 including a plurality of symbols 520. In one example, thefirst two symbols 520-a and 520-b of a second slot 515-b of a fourthsubframe 510-d may be configured as a PRACH occasion. A timing patternmay be provided that indicates a repeating pattern for the PRACHoccasion for a PRACH configuration period. As indicated above, in oneexample of resource configuration 500, the timing pattern may be aperiodic pattern where the PRACH occasion occurs within every otherradio frame 505 (e.g., during radio frames 505-a, 505-c, and 505-d).However, in other examples the PRACH occasions may occur according to anaperiodic schedule.

In some cases, one or more PRACH occasions may be configured for anextended random access request using a reduced SCS. In one example, areduced SCS or a first SCS 525 (e.g., 30 kHz) may be configured for thePRACH occasion (e.g., symbols 520-a and 520-b) and a second SCS 530(e.g., 60 kHz) may be configured for the remainder of the slot 515-b. Insuch cases, the random access request transmitted via the first symbol520-a and second symbol 520-b (e.g., using the first SCS 525) may have atime duration that is greater than the other symbols 520 that use thesecond SCS 530. In some cases, a base station may configure certainPRACH occasions with the first SCS 525 and may configure other PRACHoccasions with the second SCS 530. Accordingly, a UE may select thePRACH occasion for transmission of a random access request based onchannel conditions at the UE.

In some NR systems, PRACH occasions may be configured with 7.5 kHz SCS,15 kHz SCS, or 30 kHz SCS in frequency range 1 (FR1), which maycorrespond to non-mmW frequencies, and PRACH occasions may be configuredwith 15 kHz SCS, 30 kHz SCS, 60 kHz SCS, or 120 kHz SCS in frequencyrange 2 (FR2), which may correspond to mmW frequencies. A base stationreceiving the random access request transmitted with the reduced SCS mayhave more time during which to collect energy for each resource elementof the random access request, which may increase the likelihood ofsuccessfully decoding the random access request. In some cases, thereduced SCS PRACH occasions may be aggregated, as discussed above.

FIG. 6 illustrates an example of a process 600 that supports randomaccess coverage extension in wireless communications in accordance withaspects of the present disclosure. In some examples, process 600 mayimplement aspects of wireless communications system 100 or 200. Asindicated above, in some cases a UE may transmit extended random accessrequests, which may include aggregated random access requests that spanmultiple PRACH occasions or may include random access requeststransmitted at a smaller SCS. The example of FIG. 6 discusses aggregatedrandom access requests, although the techniques may also be applied torandom access requests transmitted at a smaller SCS.

In one example, at 605, the UE may receive PRACH configurationinformation. In some cases, PRACH configuration may be received via RMSIfrom a base station. In some examples, the PRACH configurationinformation may indicate a set of available random access preambles,where a first subset of the set of available random access preambles maybe available for aggregated random access requests and a second subsetof the set of available random access preambles may be available fornon-aggregated random access requests, where the first subset and thesecond subset may be overlapping or non-overlapping. In some cases, thePRACH configuration information may indicate that the first subset of aplurality of PRACH occasions is available for transmission of aggregatedrandom access requests, and the second subset of the plurality of PRACHoccasions is available for transmission of non-aggregated random accessrequests. In the case of overlapping subsets of PRACH occasions, randomaccess preambles may be used to differentiate aggregated versusnon-aggregated random access requests.

At 610, the UE may identify PRACH aggregation parameters. In some cases,the aggregation parameters may include a number of PRACH sequences thatare to be concatenated to span multiple PRACH occasions. In someexamples, the PRACH aggregation parameters may include different PRACHformats for different PRACH occasions. Further, in some cases, the PRACHaggregation parameters may include an indication of a signal strengththreshold value (e.g., RSRP threshold value) that may be used todetermine whether to transmit an aggregated or non-aggregated randomaccess request.

At 615, the UE may determine to transmit a random access request. Such adetermination may be made during initial system access, when the UEestablishes a connection with the base station. In some cases, the UEmay determine to transmit the random access request based on a handovercommand as part of a handover from a prior base station to the basestation that provided the PRACH configuration information. In someexamples, the UE may be in idle mode and may determine to transmit therandom access request based on a paging message received from the basestation.

At 620, the UE may measure a base station signal strength. In somecases, the UE may measure an RSRP of a reference signal transmitted bythe base station. In some cases, the reference signal may be transmittedin an SSB that is detected at the UE.

At 625, the UE may determine whether the measured signal strength meetsor exceeds a threshold value. In some cases, the threshold value may beprovided by the base station as part of the PRACH configurationinformation. In other cases, the threshold value may be preconfigured.The threshold value may be associated with a signal strength at which itbecomes less likely that a random access request from the UE will besuccessfully received at the base station in absence of an extendedrandom access request.

If the signal strength is below the threshold value, the UE may, at 630,select two or more PRACH occasions and/or a random access preamble foran aggregated random access request. As indicated above, the two or morePRACH occasions for aggregated random access requests may be indicatedin the PRACH configuration information received from the base station.In some cases, the PRACH occasions may be contiguous or non-contiguous.In some cases, the PRACH occasions may have the same or different PRACHformats.

If the signal strength is at or above the threshold value, the UE may,at 635, select one PRACH occasions and/or a random access preamble for anon-aggregated random access request.

At 640, the UE may format and transmit the random access request. Theformatting may include concatenating the random access preambles acrosstwo or more PRACH occasions when the aggregated random access request istransmitted. Additionally or alternatively, the formatting may includeformatting the random access preambles in one PRACH occasion when thenon-aggregated random access request is transmitted.

FIG. 7 illustrates an example of a process flow 700 that supports randomaccess coverage extension in wireless communications in accordance withaspects of the present disclosure. In some examples, process flow 700may implement aspects of wireless communications system 100 or 200.Process flow 700 may include UE 115-b and base station 105-b, which maybe examples of the corresponding devices described with reference toFIGS. 1 and 2.

In the following description of the process flow 700, the operationsbetween UE 115-b and base station 105-b may be transmitted in adifferent order than the order shown, or the operations performed bybase station 105-b and UE 115-b may be performed in different orders orat different times. Certain operations may also be left out of theprocess flow 700, or other operations may be added to the process flow700. It is to be understood that while base station 105-b and UE 115-bare shown performing a number of the operations of process flow 700, anywireless device may perform the operations shown.

At 705, the base station 105-b may determine PRACH configurationparameters for one or more PRACH occasions. In some cases, the PRACHconfiguration parameters may include a number of PRACH occasions, aPRACH format for the PRACH occasions, aggregation parameters for two ormore PRACH occasions, one or more SCSs for the PRACH occasions, orcombinations thereof.

At 710, the base station 105-b may transmit the PRACH configurationparameters to the UE 115-b. In some cases, some or all of the PRACHconfiguration parameters may be provided in RMSI that is received at theUE 115-b. In some examples, the PRACH configuration parameters may betransmitted via an SSB including one or more reference signals orsynchronization signals, such as a primary synchronization signal (PSS)or a secondary synchronization signal (SSS). In some cases, the PRACHconfiguration parameters may be indicated in a table or via index valuesthat are mapped to various PRACH configurations.

At 715, the UE 115-b may identify the PRACH configuration indicated bythe base station 105-b. In some cases, the PRACH configuration may beidentified based on the PRACH configuration parameters provided.

At 725, the UE 115-b may perform channel measurements. In some cases,the channel measurements may include a received signal strengthmeasurement or an RSRP measurement. In some cases, the channelmeasurements may be RSRP measurements from a reference signaltransmitted in an SSB.

At 730, the UE 115-b may determine to transmit an aggregated randomaccess request. In some cases, the determination may be made based onthe channel measurements. In some cases, if a channel measurement isbelow a threshold value the UE may determine to transmit the aggregatedrandom access request, and if the channel measurement is at or above thethreshold the UE may determine to transmit a non-aggregated randomaccess request.

At 735, the UE 115-b may determine a preamble and PRACH occasions forthe random access transmission. In some cases, the PRACH occasions maybe indicated PRACH occasions from the PRACH configuration (e.g., thatare available for aggregated random access requests). In some cases, thePRACH occasions may be contiguous or non-contiguous PRACH occasions. Insome cases, the PRACH occasions may span two or more PRACH configurationperiods. The preamble may be selected, in some cases, based on differentsubsets of preambles that are to be used for aggregated versusnon-aggregated random access requests.

At 740, the UE 115-b may aggregate the random access request. Asindicated above, the random access request may be aggregated across twoor more PRACH occasions. In some cases, the random access request may beaggregated by repeating a random access preamble sequence across each ofthe symbols in the two or more PRACH occasions.

At 745, the UE 115-b may transmit the aggregated random access requestto the base station 105-b via the two or more PRACH occasions.

At 750, the base station 105-b may combine the aggregated random accessrequest. In some cases, the base station 105-b may combine signalsreceived in each of the two or more PRACH occasions in a soft-combiningbuffer in which received energy in each of the PRACH occasions isaccumulated and used for attempting to decode the random access request.

FIG. 8 shows a block diagram 800 of a device 805 that supports randomaccess coverage extension in wireless communications in accordance withaspects of the present disclosure. The device 805 may be an example ofaspects of a UE 115 as described herein. The device 805 may include areceiver 810, a communications manager 815, and a transmitter 820. Thedevice 805 may also include a processor. Each of these components may bein communication with one another (e.g., via one or more buses).

The receiver 810 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to randomaccess coverage extension in wireless communications, etc.). Informationmay be passed on to other components of the device 805. The receiver 810may be an example of aspects of the transceiver 1120 described withreference to FIG. 11. The receiver 810 may utilize a single antenna or aset of antennas.

In some cases, the communications manager 815 may receive, from a basestation, PRACH configuration information that indicates a set of PRACHoccasions available for aggregation of random access requests andtransmit an aggregated random access request via two or more PRACHoccasions of the set of PRACH occasions.

In some cases, additionally or alternatively, the communications manager815 may also receive, from a base station, PRACH configurationinformation that indicates a set of PRACH occasions available fortransmission of random access requests, where a first subset of the setof PRACH occasions are configured with a first SCS and a second subsetof the set of PRACH occasions are configured with a second SCS that issmaller than the first SCS, and where the second subset of the set ofPRACH occasions are available for transmission of a coverage extension(CE) random access request, select two or more PRACH occasions of thesecond subset of PRACH occasions for transmission of the CE randomaccess request, and transmit the CE random access request via theselected two or more PRACH occasions. The communications manager 815 maybe an example of aspects of the communications manager 1110 describedherein.

The communications manager 815, or its sub-components, may beimplemented in hardware, code (e.g., software or firmware) executed by aprocessor, or any combination thereof. If implemented in code executedby a processor, the functions of the communications manager 815, or itssub-components may be executed by a general-purpose processor, a digitalsignal processor (DSP), an application-specific integrated circuit(ASIC), a field-programmable gate array (FPGA) or other programmablelogic device, discrete gate or transistor logic, discrete hardwarecomponents, or any combination thereof designed to perform the functionsdescribed in the present disclosure.

The communications manager 815, or its sub-components, may be physicallylocated at various positions, including being distributed such thatportions of functions are implemented at different physical locations byone or more physical components. In some examples, the communicationsmanager 815, or its sub-components, may be a separate and distinctcomponent in accordance with various aspects of the present disclosure.In some examples, the communications manager 815, or its sub-components,may be combined with one or more other hardware components, includingbut not limited to an input/output (I/O) component, a transceiver, anetwork server, another computing device, one or more other componentsdescribed in the present disclosure, or a combination thereof inaccordance with various aspects of the present disclosure.

The transmitter 820 may transmit signals generated by other componentsof the device 805. In some examples, the transmitter 820 may becollocated with a receiver 810 in a transceiver module. For example, thetransmitter 820 may be an example of aspects of the transceiver 1120described with reference to FIG. 11. The transmitter 820 may utilize asingle antenna or a set of antennas.

FIG. 9 shows a block diagram 900 of a device 905 that supports randomaccess coverage extension in wireless communications in accordance withaspects of the present disclosure. The device 905 may be an example ofaspects of a device 805 or a UE 115 as described herein. The device 905may include a receiver 910, a communications manager 915, and atransmitter 930. The device 905 may also include a processor. Each ofthese components may be in communication with one another (e.g., via oneor more buses).

The receiver 910 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to randomaccess coverage extension in wireless communications, etc.). Informationmay be passed on to other components of the device 905. The receiver 910may be an example of aspects of the transceiver 1120 described withreference to FIG. 11. The receiver 910 may utilize a single antenna or aset of antennas.

The communications manager 915 may be an example of aspects of thecommunications manager 815 as described herein. The communicationsmanager 915 may include a PRACH configuration manager 920 and a randomaccess manager 925. The communications manager 915 may be an example ofaspects of the communications manager 1110 described herein.

The PRACH configuration manager 920 may receive, from a base station,PRACH configuration information that indicates a set of PRACH occasionsavailable for aggregation of random access requests. In some cases, thePRACH configuration manager 920 may receive, from a base station, PRACHconfiguration information that indicates a set of PRACH occasionsavailable for transmission of random access requests, where a firstsubset of the set of PRACH occasions are configured with a first SCS anda second subset of the set of PRACH occasions are configured with asecond SCS that is smaller than the first SCS, and where the secondsubset of the set of PRACH occasions are available for transmission of aCE random access request. In some examples, the PRACH configurationmanager 920 may select two or more PRACH occasions of the second subsetof PRACH occasions for transmission of the CE random access request.

The random access manager 925 may transmit an aggregated random accessrequest via two or more PRACH occasions of the set of PRACH occasions.In some cases, the random access manager 925 may transmit the CE randomaccess request via the selected two or more PRACH occasions.

The transmitter 930 may transmit signals generated by other componentsof the device 905. In some examples, the transmitter 930 may becollocated with a receiver 910 in a transceiver module. For example, thetransmitter 930 may be an example of aspects of the transceiver 1120described with reference to FIG. 11. The transmitter 930 may utilize asingle antenna or a set of antennas.

FIG. 10 shows a block diagram 1000 of a communications manager 1005 thatsupports random access coverage extension in wireless communications inaccordance with aspects of the present disclosure. The communicationsmanager 1005 may be an example of aspects of a communications manager815, a communications manager 915, or a communications manager 1110described herein. The communications manager 1005 may include a PRACHconfiguration receiver 1010, a random access manager 1015, an SSBcomponent 1020. Additionally, the random access manager 1015 may includea random access preamble component 1025 and an SCS component 1035, whilethe SSB component 1020 may include a signal measurement component 1030.Each of these modules may communicate, directly or indirectly, with oneanother (e.g., via one or more buses).

The PRACH configuration receiver 1010 may receive, from a base station,PRACH configuration information 1040 that indicates a set of PRACHoccasions available for aggregation of random access requests. In someexamples, the PRACH configuration receiver 1010 may receive an RMSItransmission from the base station that includes the PRACH configurationinformation 1040. In some examples, the PRACH configuration information1040 may indicate a set of PRACH occasions available for transmission ofrandom access requests, where a first subset of the set of PRACHoccasions are configured with a first SCS and a second subset of the setof PRACH occasions are configured with a second SCS that is smaller thanthe first SCS, and where the second subset of the set of PRACH occasionsare available for transmission of a CE random access request. In someexamples, aggregated random access requests and non-aggregated randomaccess requests in an overlapping portion of the first subset and secondsubset may be differentiated based on a different set of preamblesavailable for aggregated random access requests and non-aggregatedrandom access requests.

In some cases, the set of PRACH occasions that are available foraggregation of random access requests include contiguous PRACHoccasions. In other cases, the set of PRACH occasions that are availablefor aggregation of random access requests include non-contiguous PRACHoccasions. In some cases, the PRACH configuration information 1040further includes PRACH format information, and where a first PRACHoccasion of the set of PRACH occasions has a first PRACH format, and asecond PRACH occasion of the set of PRACH occasions has a second PRACHformat. In some cases, a first subset of the set of PRACH occasions areavailable for transmission of aggregated random access requests, and asecond subset of the set of PRACH occasions are available fortransmission of non-aggregated random access requests, the first subsetbeing non-overlapping with the second subset.

In some cases, a first subset of the set of PRACH occasions areavailable for transmission of aggregated random access requests, and asecond subset of the set of PRACH occasions are available fortransmission of non-aggregated random access requests, the first subsetat least partially overlapping with the second subset. In some cases,the PRACH configuration information 1040 further includes aggregationinformation for at least a portion of the second subset of PRACHoccasions that are available for transmission of an aggregated randomaccess request that spans at least two PRACH occasions of the portion ofthe second subset of PRACH occasions. After receiving the PRACHconfiguration information 1040, the PRACH configuration receiver 1010may transmit the PRACH configuration information 1040 to random accessmanager 1015.

The SSB component 1020 may monitor for and decode SSB transmissions. Insome cases, SSB component 1020 may transmit SSB information 1050 torandom access manager 1015. The signal measurement component 1030 maymeasure a signal strength 1045 of a signal received from the basestation. In some cases, the signal strength 1045 may be an RSRPmeasurement. In some cases, the RSRP measurement may be measured from anSSB transmitted by the base station. In some examples, SSB component1020 may transmit the signal strength 1045 to the random access manager1015.

The random access manager 1015 may transmit an aggregated random accessrequest via two or more PRACH occasions of the set of PRACH occasions.In some examples, the random access manager 1015 may select the two ormore PRACH occasions from the portion of the second subset of PRACHoccasions that are available for transmission of the aggregated randomaccess request (e.g., based on the PRACH configuration information1040). In some examples, the random access manager 1015 may select twoor more PRACH occasions of the second subset of PRACH occasions fortransmission of the CE random access request. In some cases, the two ormore PRACH occasions for transmission of the aggregated random accessrequest span two or more PRACH configuration periods. In some examples,the random access manager 1015 may transmit the aggregated random accessrequest via the selected two or more PRACH occasions. In some examples,the aggregated random access request may be selected for transmissionbased on the signal strength 1045 being below a threshold value. In someexamples, the CE random access request may be transmitted based on thesignal strength 1045 being below a threshold value.

In some cases, the two or more PRACH occasions for transmission of theaggregated random access request map to an SSB (e.g., indicated in SSBinformation 1050). In some examples, the random access manager 1015 maytransmit the CE random access request via the selected two or more PRACHoccasions with a smaller SCS. In some cases, the CE random accessrequest transmitted via the second subset of PRACH occasions uses a samerandom access format as a non-CE random access request transmitted viathe first subset of PRACH occasions.

The random access preamble component 1025 may select a preamble for therandom access request. In some cases, the PRACH configurationinformation 1040 may further indicate a set of available random accesspreambles, and where a first subset of the set of available randomaccess preambles are available for aggregated random access requests anda second subset of the set of available random access preambles areavailable for non-aggregated random access requests, the first subsetbeing non-overlapping with the second subset. In some cases, theaggregated random access request includes a random access preamble thatspans each of the two or more PRACH occasions.

The SCS component 1035 may identify a SCS for the random access request.In some cases, a subset of the set of PRACH occasions have a first SCSthat is smaller than a second SCS of other of the set of PRACHoccasions. In some cases, the first SCS provides a longer symbolduration relative to the second SCS. In some cases, the second SCSprovides a longer symbol duration relative to the first SCS.

FIG. 11 shows a diagram of a system 1100 including a device 1105 thatsupports random access coverage extension in wireless communications inaccordance with aspects of the present disclosure. The device 1105 maybe an example of or include the components of device 805, device 905, ora UE 115 as described herein. The device 1105 may include components forbi-directional voice and data communications including components fortransmitting and receiving communications, including a communicationsmanager 1110, an I/O controller 1115, a transceiver 1120, an antenna1125, memory 1130, and a processor 1140. These components may be inelectronic communication via one or more buses (e.g., bus 1145).

The communications manager 1110 may receive, from a base station, PRACHconfiguration information that indicates a set of PRACH occasionsavailable for aggregation of random access requests and transmit anaggregated random access request via two or more PRACH occasions of theset of PRACH occasions. The communications manager 1110 may alsoreceive, from a base station, PRACH configuration information thatindicates a set of PRACH occasions available for transmission of randomaccess requests, where a first subset of the set of PRACH occasions areconfigured with a first SCS and a second subset of the set of PRACHoccasions are configured with a second SCS that is smaller than thefirst SCS, and where the second subset of the set of PRACH occasions areavailable for transmission of a CE random access request, select two ormore PRACH occasions of the second subset of PRACH occasions fortransmission of the CE random access request, and transmit the CE randomaccess request via the selected two or more PRACH occasions.

The I/O controller 1115 may manage input and output signals for thedevice 1105. The I/O controller 1115 may also manage peripherals notintegrated into the device 1105. In some cases, the I/O controller 1115may represent a physical connection or port to an external peripheral.In some cases, the I/O controller 1115 may utilize an operating systemsuch as iOS®, ANDROID®, MS-DOS®, MS-WINDOWS®, OS/2®, UNIX®, LINUX®, oranother known operating system. In other cases, the I/O controller 1115may represent or interact with a modem, a keyboard, a mouse, atouchscreen, or a similar device. In some cases, the I/O controller 1115may be implemented as part of a processor. In some cases, a user mayinteract with the device 1105 via the I/O controller 1115 or viahardware components controlled by the I/O controller 1115.

The transceiver 1120 may communicate bi-directionally, via one or moreantennas, wired, or wireless links as described above. For example, thetransceiver 1120 may represent a wireless transceiver and maycommunicate bi-directionally with another wireless transceiver. Thetransceiver 1120 may also include a modem to modulate the packets andprovide the modulated packets to the antennas for transmission, and todemodulate packets received from the antennas.

In some cases, the wireless device may include a single antenna 1125.However, in some cases the device may have more than one antenna 1125,which may be capable of concurrently transmitting or receiving multiplewireless transmissions.

The memory 1130 may include RAM and ROM. The memory 1130 may storecomputer-readable, computer-executable code 1135 including instructionsthat, when executed, cause the processor to perform various functionsdescribed herein. In some cases, the memory 1130 may contain, amongother things, a basic input/output system (BIOS) which may control basichardware or software operation such as the interaction with peripheralcomponents or devices.

The processor 1140 may include an intelligent hardware device, (e.g., ageneral-purpose processor, a DSP, a CPU, a microcontroller, an ASIC, anFPGA, a programmable logic device, a discrete gate or transistor logiccomponent, a discrete hardware component, or any combination thereof).In some cases, the processor 1140 may be configured to operate a memoryarray using a memory controller. In other cases, a memory controller maybe integrated into the processor 1140. The processor 1140 may beconfigured to execute computer-readable instructions stored in a memory(e.g., the memory 1130) to cause the device 1105 to perform variousfunctions (e.g., functions or tasks supporting random access coverageextension in wireless communications).

The code 1135 may include instructions to implement aspects of thepresent disclosure, including instructions to support wirelesscommunications. The code 1135 may be stored in a non-transitorycomputer-readable medium such as system memory or other type of memory.In some cases, the code 1135 may not be directly executable by theprocessor 1140 but may cause a computer (e.g., when compiled andexecuted) to perform functions described herein.

FIG. 12 shows a block diagram 1200 of a device 1205 that supports randomaccess coverage extension in wireless communications in accordance withaspects of the present disclosure. The device 1205 may be an example ofaspects of a base station 105 as described herein. The device 1205 mayinclude a receiver 1210, a communications manager 1215, and atransmitter 1220. The device 1205 may also include a processor. Each ofthese components may be in communication with one another (e.g., via oneor more buses).

The receiver 1210 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to randomaccess coverage extension in wireless communications, etc.). Informationmay be passed on to other components of the device 1205. The receiver1210 may be an example of aspects of the transceiver 1520 described withreference to FIG. 15. The receiver 1210 may utilize a single antenna ora set of antennas.

The communications manager 1215 may transmit, to a UE, PRACHconfiguration information that indicates a set of PRACH occasionsavailable for aggregation of random access requests and receive anaggregated random access request via two or more PRACH occasions of theset of PRACH occasions. The communications manager 1215 may be anexample of aspects of the communications manager 1510 described herein.

The communications manager 1215, or its sub-components, may beimplemented in hardware, code (e.g., software or firmware) executed by aprocessor, or any combination thereof. If implemented in code executedby a processor, the functions of the communications manager 1215, or itssub-components may be executed by a general-purpose processor, a DSP, anapplication-specific integrated circuit (ASIC), a FPGA or otherprogrammable logic device, discrete gate or transistor logic, discretehardware components, or any combination thereof designed to perform thefunctions described in the present disclosure.

The communications manager 1215, or its sub-components, may bephysically located at various positions, including being distributedsuch that portions of functions are implemented at different physicallocations by one or more physical components. In some examples, thecommunications manager 1215, or its sub-components, may be a separateand distinct component in accordance with various aspects of the presentdisclosure. In some examples, the communications manager 1215, or itssub-components, may be combined with one or more other hardwarecomponents, including but not limited to an input/output (I/O)component, a transceiver, a network server, another computing device,one or more other components described in the present disclosure, or acombination thereof in accordance with various aspects of the presentdisclosure.

The transmitter 1220 may transmit signals generated by other componentsof the device 1205. In some examples, the transmitter 1220 may becollocated with a receiver 1210 in a transceiver module. For example,the transmitter 1220 may be an example of aspects of the transceiver1520 described with reference to FIG. 15. The transmitter 1220 mayutilize a single antenna or a set of antennas.

FIG. 13 shows a block diagram 1300 of a device 1305 that supports randomaccess coverage extension in wireless communications in accordance withaspects of the present disclosure. The device 1305 may be an example ofaspects of a device 1205 or a base station 105 as described herein. Thedevice 1305 may include a receiver 1310, a communications manager 1315,and a transmitter 1330. The device 1305 may also include a processor.Each of these components may be in communication with one another (e.g.,via one or more buses).

The receiver 1310 may receive information such as packets, user data, orcontrol information associated with various information channels (e.g.,control channels, data channels, and information related to randomaccess coverage extension in wireless communications, etc.). Informationmay be passed on to other components of the device 1305. The receiver1310 may be an example of aspects of the transceiver 1520 described withreference to FIG. 15. The receiver 1310 may utilize a single antenna ora set of antennas.

The communications manager 1315 may be an example of aspects of thecommunications manager 1215 as described herein. The communicationsmanager 1315 may include a PRACH configuration manager 1320 and a randomaccess manager 1325. The communications manager 1315 may be an exampleof aspects of the communications manager 1510 described herein.

The PRACH configuration manager 1320 may transmit, to a UE, PRACHconfiguration information that indicates a set of PRACH occasionsavailable for aggregation of random access requests.

The random access manager 1325 may receive an aggregated random accessrequest via two or more PRACH occasions of the set of PRACH occasions.

The transmitter 1330 may transmit signals generated by other componentsof the device 1305. In some examples, the transmitter 1330 may becollocated with a receiver 1310 in a transceiver module. For example,the transmitter 1330 may be an example of aspects of the transceiver1520 described with reference to FIG. 15. The transmitter 1330 mayutilize a single antenna or a set of antennas.

FIG. 14 shows a block diagram 1400 of a communications manager 1405 thatsupports random access coverage extension in wireless communications inaccordance with aspects of the present disclosure. The communicationsmanager 1405 may be an example of aspects of a communications manager1215, a communications manager 1315, or a communications manager 1510described herein. The communications manager 1405 may include a PRACHconfiguration manager 1410, a random access receiver 1415. In somecases, PRACH configuration manager 1410 may include a signal thresholdcomponent 1420. Each of these modules may communicate, directly orindirectly, with one another (e.g., via one or more buses).

The PRACH configuration manager 1410 may transmit, to a UE, PRACHconfiguration information that indicates a set of PRACH occasionsavailable for aggregation of random access requests. In some examples,aggregated random access requests and non-aggregated random accessrequests received in an overlapping portion of the first subset andsecond subset are differentiated based on a different set of preamblesavailable for aggregated random access requests and non-aggregatedrandom access requests. In some cases, the PRACH configurationinformation further includes PRACH format information, and where a firstPRACH occasion of the set of PRACH occasions has a first PRACH format,and a second PRACH occasion of the set of PRACH occasions has a secondPRACH format.

In some cases, the PRACH configuration information further indicates aset of available random access preambles, and where a first subset ofthe set of available random access preambles are available foraggregated random access requests and a second subset of the set ofavailable random access preambles are available for non-aggregatedrandom access requests, the first subset being non-overlapping with thesecond subset. In some cases, a first subset of the set of PRACHoccasions are available for transmission of aggregated random accessrequests, and a second subset of the set of PRACH occasions areavailable for transmission of non-aggregated random access requests, thefirst subset being non-overlapping with the second subset. In somecases, a first subset of the set of PRACH occasions are available fortransmission of aggregated random access requests, and a second subsetof the set of PRACH occasions are available for transmission ofnon-aggregated random access requests, the first subset at leastpartially overlapping with the second subset.

The signal threshold component 1420 may configure a signal strengthmeasurement threshold for selection of an extended random accessrequest. In some cases, the signal strength is a RSRP measurement. Insome cases, the aggregated random access request is selected based on ameasured signal strength of a signal received at the UE from the basestation being below a threshold value. In some cases, the RSRPmeasurement is measured from an SSB transmitted by the base station.

In some examples, PRACH configuration manager 1410 may transmit PRACHreception information 1425 to random access receiver 1415, where thePRACH reception information 1425 may include information that may allowrandom access receiver 1415 to correctly receive a random access request(e.g., an aggregated random access request) and may be based on thePRACH configuration information.

The random access receiver 1415 may receive an aggregated random accessrequest via two or more PRACH occasions of the set of PRACH occasions.In some examples, the random access receiver 1415 may combine signalsreceived in the two or more PRACH occasions to detect the random accessrequest.

FIG. 15 shows a diagram of a system 1500 including a device 1505 thatsupports random access coverage extension in wireless communications inaccordance with aspects of the present disclosure. The device 1505 maybe an example of or include the components of device 1205, device 1305,or a base station 105 as described herein. The device 1505 may includecomponents for bi-directional voice and data communications includingcomponents for transmitting and receiving communications, including acommunications manager 1510, a network communications manager 1515, atransceiver 1520, an antenna 1525, memory 1530, a processor 1540, and aninter-station communications manager 1545. These components may be inelectronic communication via one or more buses (e.g., bus 1550).

The communications manager 1510 may transmit, to a UE, PRACHconfiguration information that indicates a set of PRACH occasionsavailable for aggregation of random access requests and receive anaggregated random access request via two or more PRACH occasions of theset of PRACH occasions.

The network communications manager 1515 may manage communications withthe core network (e.g., via one or more wired backhaul links). Forexample, the network communications manager 1515 may manage the transferof data communications for client devices, such as one or more UEs 115.

The transceiver 1520 may communicate bi-directionally, via one or moreantennas, wired, or wireless links as described above. For example, thetransceiver 1520 may represent a wireless transceiver and maycommunicate bi-directionally with another wireless transceiver. Thetransceiver 1520 may also include a modem to modulate the packets andprovide the modulated packets to the antennas for transmission, and todemodulate packets received from the antennas.

In some cases, the wireless device may include a single antenna 1525.However, in some cases the device may have more than one antenna 1525,which may be capable of concurrently transmitting or receiving multiplewireless transmissions.

The memory 1530 may include RAM, ROM, or a combination thereof. Thememory 1530 may store computer-readable code 1535 including instructionsthat, when executed by a processor (e.g., the processor 1540) cause thedevice to perform various functions described herein. In some cases, thememory 1530 may contain, among other things, a BIOS which may controlbasic hardware or software operation such as the interaction withperipheral components or devices.

The processor 1540 may include an intelligent hardware device, (e.g., ageneral-purpose processor, a DSP, a CPU, a microcontroller, an ASIC, anFPGA, a programmable logic device, a discrete gate or transistor logiccomponent, a discrete hardware component, or any combination thereof).In some cases, the processor 1540 may be configured to operate a memoryarray using a memory controller. In some cases, a memory controller maybe integrated into processor 1540. The processor 1540 may be configuredto execute computer-readable instructions stored in a memory (e.g., thememory 1530) to cause the device 1505 to perform various functions(e.g., functions or tasks supporting random access coverage extension inwireless communications).

The inter-station communications manager 1545 may manage communicationswith other base stations 105, and may include a controller or schedulerfor controlling communications with UEs 115 in cooperation with otherbase stations 105. For example, the inter-station communications manager1545 may coordinate scheduling for transmissions to UEs 115 for variousinterference mitigation techniques such as beamforming or jointtransmission. In some examples, the inter-station communications manager1545 may provide an X2 interface within an LTE/LTE-A wirelesscommunication network technology to provide communication between basestations 105.

The code 1535 may include instructions to implement aspects of thepresent disclosure, including instructions to support wirelesscommunications. The code 1535 may be stored in a non-transitorycomputer-readable medium such as system memory or other type of memory.In some cases, the code 1535 may not be directly executable by theprocessor 1540 but may cause a computer (e.g., when compiled andexecuted) to perform functions described herein.

FIG. 16 shows a flowchart illustrating a method 1600 that supportsrandom access coverage extension in wireless communications inaccordance with aspects of the present disclosure. The operations ofmethod 1600 may be implemented by a UE 115 or its components asdescribed herein. For example, the operations of method 1600 may beperformed by a communications manager as described with reference toFIGS. 8 to 11. In some examples, a UE may execute a set of instructionsto control the functional elements of the UE to perform the functionsdescribed below. Additionally or alternatively, a UE may perform aspectsof the functions described below using special-purpose hardware.

At 1605, the UE may receive, from a base station, PRACH configurationinformation that indicates a set of PRACH occasions available foraggregation of random access requests. For example, the PRACHconfiguration information may be received in an RMSI transmission fromthe base station that includes the PRACH configuration information. Inorder to receive the RMSI, the UE may identify time-frequency resourcesover which the RMSI is transmitted, demodulate the transmission over thetime-frequency resources, and decode the demodulated transmission toobtain bits that indicate the downlink transmission. The operations of1605 may be performed according to the methods described herein. In someexamples, aspects of the operations of 1605 may be performed by a PRACHconfiguration manager as described with reference to FIGS. 8 to 11. Insome cases, the set of PRACH occasions that are available foraggregation of random access requests include contiguous ornon-contiguous PRACH occasions. In some cases, the PRACH configurationinformation further includes PRACH format information, where a firstPRACH occasion of the set of PRACH occasions has a first PRACH format,and a second PRACH occasion of the set of PRACH occasions has a secondPRACH format. In some cases, the PRACH configuration information furtherindicates a set of available random access preambles, and where a firstsubset of the set of available random access preambles are available foraggregated random access requests and a second subset of the set ofavailable random access preambles are available for non-aggregatedrandom access requests, the first subset being non-overlapping with thesecond subset.

In some cases, a first subset of the set of PRACH occasions areavailable for transmission of aggregated random access requests, and asecond subset of the set of PRACH occasions are available fortransmission of non-aggregated random access requests, the first subsetbeing non-overlapping with the second subset. In some cases, the firstsubset of the set of PRACH occasions may be at least partiallyoverlapping with the second subset, and aggregated random accessrequests and non-aggregated random access requests in an overlappingportion of the first subset and second subset may be differentiatedbased on a different set of preambles available for aggregated randomaccess requests and non-aggregated random access requests. In somecases, a subset of the set of PRACH occasions have a first SCS that issmaller than a second SCS of other of the set of PRACH occasions.

At 1610, the UE may transmit an aggregated random access request via twoor more PRACH occasions of the set of PRACH occasions. For example, theUE may transmit the aggregated random access request via two or morePRACH occasions (e.g., chosen from the set of PRACH occasions indicatedin the PRACH configuration information), where the two or more PRACHoccasions may either be contiguous or non-contiguous. In order totransmit the aggregated random access request, the UE may identifytime-frequency resources over which the random access request is to betransmitted, may encode a set of bits containing the random accessrequest, and may modulate the encoded set of bits over the identifiedtime-frequency resources. The operations of 1610 may be performedaccording to the methods described herein. In some examples, aspects ofthe operations of 1610 may be performed by a random access manager asdescribed with reference to FIGS. 8 to 11. In some cases, the UE mayidentify a random access preamble, and aggregate the random accessrequest by repeating the random access preamble across each of the twoor more PRACH occasions.

FIG. 17 shows a flowchart illustrating a method 1700 that supportsrandom access coverage extension in wireless communications inaccordance with aspects of the present disclosure. The operations ofmethod 1700 may be implemented by a UE 115 or its components asdescribed herein. For example, the operations of method 1700 may beperformed by a communications manager as described with reference toFIGS. 8 to 11. In some examples, a UE may execute a set of instructionsto control the functional elements of the UE to perform the functionsdescribed below. Additionally or alternatively, a UE may perform aspectsof the functions described below using special-purpose hardware.

At 1705, the UE may receive, from a base station, PRACH configurationinformation that indicates a set of PRACH occasions available foraggregation of random access requests. The operations of 1705 may beperformed according to the methods described herein. In some examples,aspects of the operations of 1705 may be performed by a PRACHconfiguration manager as described with reference to FIGS. 8 to 11. Forexample, the PRACH configuration information may be received in an RMSItransmission from the base station that includes the PRACH configurationinformation. In some cases, the PRACH configuration information may bereceived via an SSB transmitted by the base station. In some cases, thePRACH configuration information may be included in a table ofconfiguration parameters, or may be indicated by one or more indexvalues that are mapped to PRACH configuration parameters. In order toreceive the, the UE may identify time-frequency resources over which thePRACH information is transmitted, demodulate the transmission over thetime-frequency resources, and decode the demodulated transmission toobtain bits that indicate the downlink transmission.

At 1710, the UE may measure a signal strength of a signal received fromthe base station. The operations of 1710 may be performed according tothe methods described herein. In some examples, aspects of theoperations of 1710 may be performed by a signal measurement component asdescribed with reference to FIGS. 8 to 11. In some cases, the signalstrength may be a RSRP measurement. In some cases, the RSRP measurementis measured from an SSB transmitted by the base station.

At 1715, the UE may select the aggregated random access request fortransmission based on the signal strength being below a threshold value.For example, the UE may select the aggregated random access requestbased on the PRACH configuration information (e.g., data bits) receivedfrom the base station (e.g., the UE may select an aggregated randomaccess request indicated by the base station). The operations of 1725may be performed according to the methods described herein. In someexamples, aspects of the operations of 1725 may be performed by a signalmeasurement component as described with reference to FIGS. 8 to 11.

At 1720, the UE may transmit the selected aggregated random accessrequest via two or more PRACH occasions of the set of PRACH occasions.For example, the UE may transmit the aggregated random access requestvia two or more PRACH occasions (e.g., chosen from the set of PRACHoccasions indicated in the PRACH configuration information), where thetwo or more PRACH occasions may either be contiguous or non-contiguous.In order to transmit the aggregated random access request, the UE mayidentify time-frequency resources over which the random access requestis to be transmitted, may encode a set of bits containing the randomaccess request, and may modulate the encoded set of bits over theidentified time-frequency resources. The operations of 1730 may beperformed according to the methods described herein. In some examples,aspects of the operations of 1730 may be performed by a random accessmanager as described with reference to FIGS. 8 to 11. In some cases, theUE may identify a random access preamble, and aggregate the randomaccess request by repeating the random access preamble across each ofthe two or more PRACH occasions.

FIG. 18 shows a flowchart illustrating a method 1800 that supportsrandom access coverage extension in wireless communications inaccordance with aspects of the present disclosure. The operations ofmethod 1800 may be implemented by a UE 115 or its components asdescribed herein. For example, the operations of method 1800 may beperformed by a communications manager as described with reference toFIGS. 8 to 11. In some examples, a UE may execute a set of instructionsto control the functional elements of the UE to perform the functionsdescribed below. Additionally or alternatively, a UE may perform aspectsof the functions described below using special-purpose hardware.

At 1805, the UE may receive, from a base station, PRACH configurationinformation. For example, the PRACH configuration information may bereceived in an RMSI transmission from the base station that includes thePRACH configuration information. In some cases, the PRACH configurationinformation may be received via an SSB transmitted by the base station.In some cases, the PRACH configuration information may be included in atable of configuration parameters, or may be indicated by one or moreindex values that are mapped to PRACH configuration parameters. In orderto receive the, the UE may identify time-frequency resources over whichthe PRACH information is transmitted, demodulate the transmission overthe time-frequency resources, and decode the demodulated transmission toobtain bits that indicate the downlink transmission.

In some cases, the PRACH configuration information may indicate a set ofPRACH occasions available for transmission of random access requests,where a first subset of the set of PRACH occasions are configured with afirst SCS and a second subset of the set of PRACH occasions areconfigured with a second SCS that is smaller than the first SCS, andwhere the second subset of the set of PRACH occasions are available fortransmission of a CE random access request. The operations of 1805 maybe performed according to the methods described herein. In someexamples, aspects of the operations of 1805 may be performed by a PRACHconfiguration manager as described with reference to FIGS. 8 to 11.

At 1810, the UE may optionally measure a signal strength of a signalreceived from the base station. The operations of 1810 may be performedaccording to the methods described herein. In some examples, aspects ofthe operations of 1810 may be performed by a signal measurementcomponent as described with reference to FIGS. 8 to 11. In some cases,the signal strength is a RSRP measurement. In some cases, the RSRPmeasurement is measured from a SSB transmitted by the base station.

At 1815, the UE may optionally determine that the CE random accessrequest is to be transmitted based on the signal strength being below athreshold value. The operations of 1815 may be performed according tothe methods described herein. In some examples, aspects of theoperations of 1815 may be performed by a signal measurement component asdescribed with reference to FIGS. 8 to 11. The CE random access requestmay be transmitted at the second SCS, and which may provide a longerduration random access request.

At 1820, the UE may select two or more PRACH occasions of the secondsubset of PRACH occasions for transmission of the CE random accessrequest. For example, the UE may select the aggregated random accessrequest based on the PRACH configuration information (e.g., data bits)received from the base station (e.g., the UE may select an aggregatedrandom access request indicated by the base station). The operations of1820 may be performed according to the methods described herein. In someexamples, aspects of the operations of 1820 may be performed by a PRACHconfiguration manager as described with reference to FIGS. 8 to 11.

At 1825, the UE may transmit the CE random access request via theselected two or more PRACH occasions. For example, the UE may transmitthe aggregated random access request via two or more PRACH occasions(e.g., chosen from the set of PRACH occasions indicated in the PRACHconfiguration information), where the two or more PRACH occasions mayeither be contiguous or non-contiguous. In order to transmit theaggregated random access request, the UE may identify time-frequencyresources over which the random access request is to be transmitted, mayencode a set of bits containing the random access request, and maymodulate the encoded set of bits over the identified time-frequencyresources. The operations of 1825 may be performed according to themethods described herein. In some examples, aspects of the operations of1825 may be performed by a random access manager as described withreference to FIGS. 8 to 11. In some cases, the CE random access requesttransmitted via the second subset of PRACH occasions uses a same randomaccess format as a non-CE random access request transmitted via thefirst subset of PRACH occasions.

It should be noted that the methods described above describe possibleimplementations, and that the operations and the steps may be rearrangedor otherwise modified and that other implementations are possible.Further, aspects from two or more of the methods may be combined.

Techniques described herein may be used for various wirelesscommunications systems such as code division multiple access (CDMA),time division multiple access (TDMA), frequency division multiple access(FDMA), orthogonal frequency division multiple access (OFDMA), singlecarrier frequency division multiple access (SC-FDMA), and other systems.A CDMA system may implement a radio technology such as CDMA2000,Universal Terrestrial Radio Access (UTRA), etc. CDMA2000 covers IS-2000,IS-95, and IS-856 standards. IS-2000 Releases may be commonly referredto as CDMA2000 1×, 1×, etc. IS-856 (TIA-856) is commonly referred to asCDMA2000 1xEV-DO, High Rate Packet Data (HRPD), etc. UTRA includesWideband CDMA (WCDMA) and other variants of CDMA. A TDMA system mayimplement a radio technology such as Global System for MobileCommunications (GSM).

An OFDMA system may implement a radio technology such as Ultra MobileBroadband (UMB), Evolved UTRA (E-UTRA), Institute of Electrical andElectronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE802.20, Flash-OFDM, etc. UTRA and E-UTRA are part of Universal MobileTelecommunications System (UMTS). LTE, LTE-A, and LTE-A Pro are releasesof UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, LTE-A Pro, NR,and GSM are described in documents from the organization named “3rdGeneration Partnership Project” (3GPP). CDMA2000 and UMB are describedin documents from an organization named “3rd Generation PartnershipProject 2” (3GPP2). The techniques described herein may be used for thesystems and radio technologies mentioned above as well as other systemsand radio technologies. While aspects of an LTE, LTE-A, LTE-A Pro, or NRsystem may be described for purposes of example, and LTE, LTE-A, LTE-APro, or NR terminology may be used in much of the description, thetechniques described herein are applicable beyond LTE, LTE-A, LTE-A Pro,or NR applications.

A macro cell generally covers a relatively large geographic area (e.g.,several kilometers in radius) and may allow unrestricted access by UEs115 with service subscriptions with the network provider. A small cellmay be associated with a lower-powered base station 105, as comparedwith a macro cell, and a small cell may operate in the same or different(e.g., licensed, unlicensed, etc.) frequency bands as macro cells. Smallcells may include pico cells, femto cells, and micro cells according tovarious examples. A pico cell, for example, may cover a small geographicarea and may allow unrestricted access by UEs 115 with servicesubscriptions with the network provider. A femto cell may also cover asmall geographic area (e.g., a home) and may provide restricted accessby UEs 115 having an association with the femto cell (e.g., UEs 115 in aclosed subscriber group (CSG), UEs 115 for users in the home, and thelike). An eNB for a macro cell may be referred to as a macro eNB. An eNBfor a small cell may be referred to as a small cell eNB, a pico eNB, afemto eNB, or a home eNB. An eNB may support one or multiple (e.g., two,three, four, and the like) cells, and may also support communicationsusing one or multiple component carriers.

The wireless communications system 100 or systems described herein maysupport synchronous or asynchronous operation. For synchronousoperation, the base stations 105 may have similar frame timing, andtransmissions from different base stations 105 may be approximatelyaligned in time. For asynchronous operation, the base stations 105 mayhave different frame timing, and transmissions from different basestations 105 may not be aligned in time. The techniques described hereinmay be used for either synchronous or asynchronous operations.

Information and signals described herein may be represented using any ofa variety of different technologies and techniques. For example, data,instructions, commands, information, signals, bits, symbols, and chipsthat may be referenced throughout the above description may berepresented by voltages, currents, electromagnetic waves, magneticfields or particles, optical fields or particles, or any combinationthereof.

The various illustrative blocks and modules described in connection withthe disclosure herein may be implemented or performed with ageneral-purpose processor, a digital signal processor (DSP), anapplication-specific integrated circuit (ASIC), a field-programmablegate array (FPGA) or other programmable logic device (PLD), discretegate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.A general-purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices (e.g., a combinationof a DSP and a microprocessor, multiple microprocessors, one or moremicroprocessors in conjunction with a DSP core, or any other suchconfiguration).

The functions described herein may be implemented in hardware, softwareexecuted by a processor, firmware, or any combination thereof. Ifimplemented in software executed by a processor, the functions may bestored on or transmitted over as one or more instructions or code on acomputer-readable medium. Other examples and implementations are withinthe scope of the disclosure and appended claims. For example, due to thenature of software, functions described above can be implemented usingsoftware executed by a processor, hardware, firmware, hardwiring, orcombinations of any of these. Features implementing functions may alsobe physically located at various positions, including being distributedsuch that portions of functions are implemented at different physicallocations.

Computer-readable media includes both non-transitory computer storagemedia and communication media including any medium that facilitatestransfer of a computer program from one place to another. Anon-transitory storage medium may be any available medium that can beaccessed by a general purpose or special purpose computer. By way ofexample, and not limitation, non-transitory computer-readable media mayinclude random-access memory (RAM), read-only memory (ROM), electricallyerasable programmable read only memory (EEPROM), flash memory, compactdisk (CD) ROM or other optical disk storage, magnetic disk storage orother magnetic storage devices, or any other non-transitory medium thatcan be used to carry or store desired program code means in the form ofinstructions or data structures and that can be accessed by ageneral-purpose or special-purpose computer, or a general-purpose orspecial-purpose processor. Also, any connection is properly termed acomputer-readable medium. For example, if the software is transmittedfrom a website, server, or other remote source using a coaxial cable,fiber optic cable, twisted pair, digital subscriber line (DSL), orwireless technologies such as infrared, radio, and microwave, then thecoaxial cable, fiber optic cable, twisted pair, DSL, or wirelesstechnologies such as infrared, radio, and microwave are included in thedefinition of medium. Disk and disc, as used herein, include CD, laserdisc, optical disc, digital versatile disc (DVD), floppy disk andBlu-ray disc where disks usually reproduce data magnetically, whilediscs reproduce data optically with lasers. Combinations of the aboveare also included within the scope of computer-readable media.

As used herein, including in the claims, “or” as used in a list of items(e.g., a list of items prefaced by a phrase such as “at least one of” or“one or more of”) indicates an inclusive list such that, for example, alist of at least one of A, B, or C means A or B or C or AB or AC or BCor ABC (i.e., A and B and C). Also, as used herein, the phrase “basedon” shall not be construed as a reference to a closed set of conditions.For example, an exemplary step that is described as “based on conditionA” may be based on both a condition A and a condition B withoutdeparting from the scope of the present disclosure. In other words, asused herein, the phrase “based on” shall be construed in the same manneras the phrase “based at least in part on.”

In the appended figures, similar components or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If just the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label, or othersubsequent reference label.

The description set forth herein, in connection with the appendeddrawings, describes example configurations and does not represent allthe examples that may be implemented or that are within the scope of theclaims. The term “exemplary” used herein means “serving as an example,instance, or illustration,” and not “preferred” or “advantageous overother examples.” The detailed description includes specific details forthe purpose of providing an understanding of the described techniques.These techniques, however, may be practiced without these specificdetails. In some instances, well-known structures and devices are shownin block diagram form in order to avoid obscuring the concepts of thedescribed examples.

The description herein is provided to enable a person skilled in the artto make or use the disclosure. Various modifications to the disclosurewill be readily apparent to those skilled in the art, and the genericprinciples defined herein may be applied to other variations withoutdeparting from the scope of the disclosure. Thus, the disclosure is notlimited to the examples and designs described herein, but is to beaccorded the broadest scope consistent with the principles and novelfeatures disclosed herein.

What is claimed is:
 1. A method for wireless communication at a userequipment (UE), comprising: receiving, from a base station, physicalrandom access channel (PRACH) configuration information that indicates aplurality of PRACH occasions available for aggregation of random accessrequests; and transmitting an aggregated random access request via twoor more PRACH occasions of the plurality of PRACH occasions.
 2. Themethod of claim 1, further comprising: measuring a signal strength of asignal received from the base station; and selecting the aggregatedrandom access request for transmission based at least in part on thesignal strength being below a threshold value.
 3. The method of claim 2,wherein the signal strength is a reference signal received power (RSRP)measurement.
 4. The method of claim 3, wherein the RSRP measurement ismeasured from a synchronization signal block (SSB) transmitted by thebase station.
 5. The method of claim 1, wherein the plurality of PRACHoccasions that are available for aggregation of random access requestscomprise contiguous PRACH occasions.
 6. The method of claim 1, whereinthe plurality of PRACH occasions that are available for aggregation ofrandom access requests comprise non-contiguous PRACH occasions.
 7. Themethod of claim 1, wherein the PRACH configuration information furtherincludes PRACH format information, and wherein a first PRACH occasion ofthe plurality of PRACH occasions has a first PRACH format, and a secondPRACH occasion of the plurality of PRACH occasions has a second PRACHformat.
 8. The method of claim 1, wherein the PRACH configurationinformation further indicates a set of available random accesspreambles, and wherein a first subset of the set of available randomaccess preambles are available for aggregated random access requests anda second subset of the set of available random access preambles areavailable for non-aggregated random access requests, the first subsetbeing non-overlapping with the second subset.
 9. The method of claim 1,wherein a first subset of the plurality of PRACH occasions are availablefor transmission of aggregated random access requests, and a secondsubset of the plurality of PRACH occasions are available fortransmission of non-aggregated random access requests, the first subsetbeing non-overlapping with the second subset.
 10. The method of claim 1,wherein a first subset of the plurality of PRACH occasions are availablefor transmission of aggregated random access requests, and a secondsubset of the plurality of PRACH occasions are available fortransmission of non-aggregated random access requests, the first subsetat least partially overlapping with the second subset.
 11. The method ofclaim 1, wherein the receiving further comprises: receiving a remainingminimum system information (RMSI) transmission from the base stationthat includes the PRACH configuration information.
 12. The method ofclaim 1, wherein the two or more PRACH occasions for transmission of theaggregated random access request map to a same synchronization signalblock (SSB).
 13. The method of claim 1, wherein the two or more PRACHoccasions for transmission of the aggregated random access request spantwo or more PRACH configuration periods.
 14. The method of claim 1,wherein the aggregated random access request comprises a random accesspreamble that spans each of the two or more PRACH occasions.
 15. Themethod of claim 1, wherein a subset of the plurality of PRACH occasionshave a first subcarrier spacing (SCS) that is smaller than a second SCSof other of the plurality of PRACH occasions.
 16. The method of claim15, wherein the first SCS provides a longer symbol duration relative tothe second SCS.
 17. A method for wireless communication, comprising:receiving, from a base station, physical random access channel (PRACH)configuration information that indicates a plurality of PRACH occasionsavailable for transmission of random access requests, wherein a firstsubset of the plurality of PRACH occasions are configured with a firstsubcarrier spacing (SCS) and a second subset of the plurality of PRACHoccasions are configured with a second SCS that is smaller than thefirst SCS, and wherein the second subset of the plurality of PRACHoccasions are available for transmission of a coverage extension (CE)random access request; selecting two or more PRACH occasions of thesecond subset of PRACH occasions for transmission of the CE randomaccess request; and transmitting the CE random access request via theselected two or more PRACH occasions.
 18. The method of claim 17,wherein the CE random access request transmitted via the second subsetof PRACH occasions uses a same random access format as a non-CE randomaccess request transmitted via the first subset of PRACH occasions. 19.The method of claim 17, wherein the second SCS provides a longer symbolduration relative to the first SCS.
 20. The method of claim 17, furthercomprising: measuring a signal strength of a signal received from thebase station; and determining that the CE random access request is to betransmitted based at least in part on the signal strength being below athreshold value.
 21. The method of claim 20, wherein the signal strengthis a reference signal received power (RSRP) measurement.
 22. The methodof claim 17, wherein the PRACH configuration information furthercomprises aggregation information for at least a portion of the secondsubset of PRACH occasions that are available for transmission of anaggregated random access request that spans at least two PRACH occasionsof the portion of the second subset of PRACH occasions.
 23. The methodof claim 22, wherein the selecting further comprises: selecting the twoor more PRACH occasions from the portion of the second subset of PRACHoccasions that are available for transmission of the aggregated randomaccess request; and transmitting the aggregated random access requestvia the selected two or more PRACH occasions.
 24. An apparatus forwireless communication at a user equipment (UE), comprising: aprocessor, memory in electronic communication with the processor; andinstructions stored in the memory and executable by the processor tocause the apparatus to: receive, from a base station, physical randomaccess channel (PRACH) configuration information that indicates aplurality of PRACH occasions available for aggregation of random accessrequests; and transmit an aggregated random access request via two ormore PRACH occasions of the plurality of PRACH occasions.
 25. Theapparatus of claim 24, wherein the instructions are further executableby the processor to cause the apparatus to: measure a signal strength ofa signal received from the base station; and select the aggregatedrandom access request for transmission based at least in part on thesignal strength being below a threshold value.
 26. The apparatus ofclaim 24, wherein the PRACH configuration information further includesPRACH format information, and wherein a first PRACH occasion of theplurality of PRACH occasions has a first PRACH format, and a secondPRACH occasion of the plurality of PRACH occasions has a second PRACHformat.
 27. The apparatus of claim 24, wherein the PRACH configurationinformation further indicates a set of available random accesspreambles, and wherein a first subset of the set of available randomaccess preambles are available for aggregated random access requests anda second subset of the set of available random access preambles areavailable for non-aggregated random access requests, the first subsetbeing non-overlapping with the second subset.
 28. The apparatus of claim24, wherein the two or more PRACH occasions for transmission of theaggregated random access request span two or more PRACH configurationperiods.
 29. An apparatus for wireless communication, comprising: aprocessor, memory in electronic communication with the processor; andinstructions stored in the memory and executable by the processor tocause the apparatus to: receive, from a base station, physical randomaccess channel (PRACH) configuration information that indicates aplurality of PRACH occasions available for transmission of random accessrequests, wherein a first subset of the plurality of PRACH occasions areconfigured with a first subcarrier spacing (SCS) and a second subset ofthe plurality of PRACH occasions are configured with a second SCS thatis smaller than the first SCS, and wherein the second subset of theplurality of PRACH occasions are available for transmission of acoverage extension (CE) random access request; select two or more PRACHoccasions of the second subset of PRACH occasions for transmission ofthe CE random access request; and transmit the CE random access requestvia the selected two or more PRACH occasions.
 30. The apparatus of claim29, wherein the CE random access request transmitted via the secondsubset of PRACH occasions uses a same random access format as a non-CErandom access request transmitted via the first subset of PRACHoccasions and the second SCS of the second subset of PRACH occasionsprovides a longer symbol duration relative to the first SCS of the firstsubset of PRACH occasions.